Bio 3950 updated: FA09
Vertebrate
Natural History
Introduction
A. How does science work? Hypothetico-deductive
reasoning:
1. Observation
2. Hypothesis -- this proposes a possible cause (or several causes)
3. Test hypothesis
4. Retain/Refute/Revise hypothesis
(5. Retest revised hypothesis)
All hypotheses: (a)
should be testable; and, (b) can be eliminated via testing.
Biological
phenomena are based on a hierarchical organization of living things, the
structures within them, and the roles they play in the environment -- subatomic
particles & atoms > molecules > organelles > cells > tissues
> organs > systems > multicellular organisms
> populations > communities > ecosystems > biomes > biosphere
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Distinction & Classification
Taxonomic
hierarchy:
Kingdom, Phylum, Class, Order, Family,
Genus, species
The
hierarchy is based on a system called binomial nomenclature. This system assigns each organismal
species with a two-part Latin name -- a Genus name, and a specific epithet. However, no two species have the same
binomial epithet.
Why is there so much
diversity? Why are there two
different types of bacteria/mushrooms/snakes/etc. in a particular place on Earth, when there just as easily
could be one?? Historical changes
in environmental conditions have caused changes in ancestral forms of organisms
which produced more than one type of descendant.
Evolution by process
of natural selection --
:
the environment changes
:
organisms produce far more offspring than are capable of surviving
:
some of those offspring possess traits which are better suited for the current
environmental conditions than others.
:
those offspring better adapted to current environmental conditions will
out-compete those which are not for available resources, and hence survive to
reproduce (this passes their genes on to future generations).
An important concept to grasp about evolutionary
processes is TIME, and an appreciation for how much of it must elapse in
order to produce evolutionary change.
One global concern is human activities
accelerating the rate of environmental change to a level where other organisms
cannot keep pace and thus go extinct.
Evolutionary History
& Biogeography
Global
conditions past & present –
4.8
bya = formation of Earth
2.6
bya = 1st alg¾,
beginning of 02 build-up in atmosphere
1.6
bya = 1st eukaryotes; Pang¾a
formation begins
680
mya = 1st multicellular
organisms, rapid radiation during Cambrian
525
mya = 1st vertebrate ancestor
500
mya = 1st fish ancestor
440
mya = 1st land plants
415
mya = 1st land invertebrates
360
mya = 1st amphibians, trees; beginning of
coal deposit formation
320
mya = 1st reptiles; Pang¾a
formation complete; Permian-Triassic extinction (of 83% of known Genera)
210
mya = Triassic-Jurassic extinction (of 48 % of known
Genera); 1st marsupials, birds
140
mya = 1st angiosperms; Pang¾a
breaks into Laurasia (N hemisphere) and Gondwonaland (S hemisphere)
65
mya = Alp and Rocky Mtn orogeny; 1st placentals;
Cretaceous-Tertiary extinction (of 50 % of known Genera)
4.8
mya = 1st hominids; polar ice cap
formation
1.2
mya = Homo
erectus, tool use;1st of repeated glaciations
10
- 0.5 kya = anthropogenic extinction of Australian
(85 %), North American (60 %), Madagascan/New Zealand (99 %) fauna.
The climate (temp., precip., photoperiod, wind)
on any particular region affects the organisms found there. Local climates can be affected by (a)
latitude, (b) proximity to ocean, and (c) altitudinal barriers. Global climates have changed during
Earth's history (& effected taxa distribution)
b/c:
a)
plate tectonics –continents are "floating" on viscous
mantle pool. @ time 1st
vertebrates, 1 of 2 major continents of Pre-Cambrian (Laurasia)
6 broken up into 5 smaller continents; this facilitated taxa
radiation.
b) glaciation – changes in polar ice area affect sea
level, and therefore, climate & exposed land area.
Biogeographic
Rules affecting extant endothermic taxa.
1.
Bergman's Rule: greater indiv. size @ higher
latitude, b/c lower temp. means indiv's should have
lower SA:V to conserve heat.
2. Allen's
Rule: shorter extremities in areas w/ greater temp. fluctuation b/c indiv's should have lower SA:V to conserve heat.
3. Gloger's Rule: indiv. w/ darker
color in warm/humid areas, b/c there is more shading in tropics
4. Fahrenholz's Rule: symbiotic spp. (e.g., parasite-host) tend to evolve together, so similar spp.
should have similar symbionts.
How do you tell the difference between taxonomic
groups?
a) morphology: similar measurements on variety of char's = relatedness
b) behavior: similar postures/displays/strategies
= close relatedness
c) ecology: similar habitat req's,
interspp. assoc. = close relatedness
d) biochemical: genetic similarity = relatedness
If these rules can be used to explain size
variation between popln's of indiv's
w/in spp., then what explains sexual size dimorphism?
1.
F needs to eat more prey to produce larger gametes
2.
F needs to be larger to produce larger clutch size
3.
F needs to be larger to avoid injury during ritualized courtship display
4.
F needs to be larger to incubate clutch (oviparous taxa
only)
5.
M needs to be larger to defend resources
6.
dichotomy exists to reduce competition for other resources.
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Phylum Chordata – four common features
(a) notochord - attachment site for
muscles
(b) nerve cord - nervous system, may
have anterior development (brain)
(c) pharyngeal gill slits - may form
respiratory structures or be vestigial
(d) post-anal tail - may be vestigial
Subphylum Urochordata – filter-feeding
tunicates w/ "tadpole" larv¾; paedomorphic larval form gave rise to
other chordates.
Subphylum Cephalochordata – lancelets w/
segmented myomeres that aid in movement; gill slits for feeding (not respirat'n) & open circulatory system.
Subphylum Vertebrata – shared features
(a) vertebrae – serially arranged along
dorsum = cartilage, bone (or absent)
(b) cranium – a skull surrounding brain =
fibrous, cartilage, or bone
(c) neural crest – embryonic tissue that
forms novel structures (esp. in head)
(d) enlarged, tripartite brain
These structures manifested increased size and
activity levels in vertebrates which in turn promoted other adaptations:
pharyngeal gills (fewer in #, but more complex) for respirat'n,
true heart, muscularized g.i.
tract, & discrete visceral organs (e.g.,
kidney, liver, pancreas).
Based on fossil evidence & physiology of
extant forms, the 1st vertebrates arose in marine environments. Among early taxa, ostracoderms
were 1st to have bone (head plates) and glomerular
kidney for Ca+2 and P+2 uptake. Extant analogy = Superfamily Myxinoidea
(extant hagfish) w/ equal ion concentration as seawater but w/out bone seen as
proto-vertebrate condition.
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The Unity of Structure
Embryological system development
1.
zygote – fertilized egg
2.
blastula – formation of primitive coelom
(hollow ball of many cells)
3.
gastrula – formation of three tissue layers (3-layered ball)
a)
ectoderm forms superficial layers, g.i. tract,
nervous/sensory organs
b)
endoderm forms g.i. tract & assoc. glands (e.g., liver, pancreas).
c)
mesoderm forms muscle, skeletal, circulatory, urogenital organs
4.
neurula – formation of notochord & dorsal nerve chord from
ectoderm.
The germ layers lead
to different tissue types:
1. Epithelial -- (a)
membranous, func. for coverage
(b) glands: i.
Endocrine glands secrete hormones into extracellular space
ii. Exocrine glands
secrete material directly to target organ or outside body.
2. Connective --
tendons/ligaments func. for support
3. Vascular –
circulate blood, gases, wastes
4. Muscle -- ability
to contract for movement function
5. Nervous -- ability
to conduct e- signals for sensory function.
Structural/protective
elements......
Components of skeletal
tissue:
1. cartilage --
embryonic bone; living cells that provide flexible support and connections
between bones.
2. compact bone --
dense, strong bone serving as attachment site for muscles.
3. spongy bone --
porous, light-weight, highly-vascularized; bone marrow is located in the
cavities and this is where blood cells are formed.
Divisions of the
skeletal system:
1. appendicular -- the
bones of the appendages (girdles & limbs)
2. axial -- the bones
of the central axis (skull, spinal column, & ribs).
Functions of
vertebrate skeleton:
1. support/protection
of visceral organs in body as well as attachment site for muscle tissue.
2. production of cells
in blood, including erythrocytes, leukocytes, platelets.
3. storage site for Ca
and P
4. sensory perception
-- the bones of the middle ear that transmit sound.
Specialized bone type
– teeth are a highly-mineralized combo. of bone, enamel, and
dentine. Types of root systems:
1. acrodont –
fused to top of jaw margin
2. pleurodont
– set on shelf on medial side of jaw
3. thecodont –
set in sockets
Body movement
is accomplished by muscles attaching to bones w/ bands of connective tissue
called tendons. Skeletal muscles
are arranged in antagonistic pairs such that the contraction of one muscle to
flex a joint can be reversed by the contraction of another muscle to extend the
same joint.
Types of muscle
tissue:
1. skeletal muscle --
multinucleate, striated, voluntary contractions
2. smooth muscle -- mononucleate, non-striated, involuntary contraction, moves
stuff through hollow organs.
3. cardiac muscle -- multinucleate,
semi-striated, involuntary control
Muscle fiber (cell)
structure consists of several subunits called myofibrils each of which has
hundreds of bands of protein chains.
One protein type, myosin, attaches to another protein type, actin, and
pulls the two actin chains together, thus shortening the muscle.
The muscle fibers are
stimulated by electrical signals from motor neurons.
Vertebrate muscular
systems divided into 2 broad regions:
1. axial –
folded blocks originating from the spinal column, 1¡ support
(a) epaxial – those articulating
dorsal to the spinal column
(b) hypaxial – those articulating
ventral to the spinal column
2. appendicular
– originating from limb bones, 1¡ locomotion
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The Unity of Function
Acquisition of nutrients
is a multi-step process:
1. ingestion -- food
is brought into the mouth
2. digestion --
chemical breakdown via enzymes, acids and mastication (mechanical breakdown of
food, typically w/ teeth)
4. absorption --
transport of small molecules (including water) from digestive cavity into cells
or circulatory system.
5. elimination --
indigestible materials are expelled from the body.
Pathway of food: mouth
(mastication, digestion of starch), to esophagus, to stomach (digestion of
protein), to small intestine (digestion of fats & sugars, absorption), to
large intestine (absorption), rectum, anus.
Accessory digestive
organs:
1. salivary glands --
in mouth, secrete enzyme to digest starch.
2. Gall bladder --
w/in liver, produces bile salts to digest fats.
3. pancreas --
secretes enzymes to digest sugars, fats, and proteins.
If the stomach is
acidic, why don't we digest ourselves?
1. cells lining
stomach not only produce HCl, but also mucous to
neutralize acid.
2. cells lining
stomach are replaced much more rapidly than other cell types.
3. cells lining
stomach have many tight junctions so that acid doesn't leak out.
What about when acidic
contents leave the stomach?
4. pancreas secretes
basic sol'n to neutralize acid and continue
digestion.
All respiratory
systems share two characteristics:
1. a moist respiratory
surface to facilitate gas exchange (gases must be dissolved in liquid in order
to enter/exit living cells).
2. a relatively large
surface area in contact with the environment (to allow for adequate rates of
the diffusion of gases).
Pathway of air into
the lungs -- From the nose/mouth, air enters pharynx, to larynx (containing
vocal cords), to trachea, to bronchi, to bronchioles, to alveoli where gas
exchange with capillaries occurs.
A single alveolus and the adjacent capillary are
each only 1 cell layer thick, such that is it easy for O2 to diffuse
across into the blood stream. The
bond between O2 and Hb is weak and
reversible, such that when in the tissues, O2 can be released to the
cells for respiration. Some O2
is replaced by CO2, but most of the CO2 molecules are
converted into bicarbonate ions (-HCO3) for transport to the lungs.
Breathing cycle:
1. Inhalation
accomplished by making chest cavity larger via diaphragm and intercostal muscle contraction.
2. The enlarged cavity
generates negative pressure in lungs which draws air inwards.
3. Exhalation occurs
when these muscles relax, compressing the chest cavity, and forcing air out of
the lungs.
Functions of the circulatory
system:
1. gas transport &
exchange
2. distribution of
nutrients from digestive system to other body areas
3. transport of
toxins/wastes to liver (detoxification) & kidneys (excretion)
4. distribution of
hormones from endocrine glands to target tissue.
5. regulation of body
temperature
6. initial wound
healing through clot formation
7. protection from
infection via distribution of antibodies & leukocytes.
Blood elements --
formed elements from bone marrow
1. erythrocytes (red
blood cells), anucleate, transport gases.
2. leukocytes (white
blood cells), nucleate, protect body from foreign material
3. platelets
(fragments of megakaryocytes), anucleate,
cause blood clotting
-- plasma is the fluid
bathing the formed elements that contains proteins (immune, clotting, osmotic
function), salts, hormones, nutrients, and gases.
Flow of blood in
mammalian body:
1. blood leaves right
ventricle via pulmonary artery to go to lungs where CO2 can be
exchanged for O2 in capillary beds of lungs.
2. blood from lungs
enters left atrium via pulmonary vein (still w/ O2).
3. blood from left
atrium enters left ventricle
4. blood leaves left
ventricle via aorta to go to body where it can exchange O2 for CO2
in capillary beds.
5. in body, blood goes
from aorta to arteries, to arterioles, to capillaries (gas exchange occurs
here), to venules, to veins to the vena cava and back
to heart.
6. blood from body (w/
CO2) enters right atrium via vena cava (large vein).
7. blood from right
atrium enters right ventricle
What keeps the blood
flowing in the same direction?
1. valves separating atrial & ventricular chambers prevent backflow when
heart contracts.
2. valves in veins
that prevent backflow as blood returns to heart.
3. muscle contraction
around veins pushes blood through valves towards heart.
Evolution of heart
structure:
á
2-chambered in fish w/out separation of O2
and de-O2 blood.
á
3-chambered in amphibians & some
reptiles w/ partial separation of O2 and de-O2 blood for
more effective gas transport.
á
4-chambered in crocs., birds, &
mammals w/ complete separation of O2 and de-O2 blood.
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The Unity of
Regulation
The excretory
system is effective at several functions:
1. elimination of
digestive waste products.
2. regulation of water
content in plasma.
3. regulation of ion
balance in plasma (esp. Na+, K+, Cl-,
Ca+2).
4. regulation of pH of
blood.
5. retention of
nutrients in blood (esp. sugars and amino acids).
6. secretion of
hormones to promote erythrocyte formation.
Pathway of urine
formation in kidney:
1. blood enters the
kidney via renal artery which branches to form a capillary bed called the glomerulus.
Water, nutrients, and waste are filtered from the capillary into part of
the nephron called the Bowman's capsule.
2. The filtrate then
passes along the loop of Henle that is entwined with
the capillaries that left the glomerulus. Nutrients and most of the water are
reabsorbed into blood. Also,
additional wastes are actively transported into the nephron tubule.
3. The wastes are then
concentrated in the collecting duct of the nephron which drains to the ureter connecting the kidney to the bladder. This concentration results in a urine
solution that is hyperosmotic (4x) to the blood in
the surrounding capillaries.
4. The bladder is
drained by the urethra that transports the urine out of body.
5. blood containing
required concentrations of water, nutrients, and ions returns to the rest of
the circulatory system via renal vein.
Not all vertebrates use the same structures
within kidney which has two functional units: pronephros & opisthonephros
(= meso- + meta- nephros).
(a) all embryonic forms use pronephros
(b) nonamniotic adults
use segmented opisthonephros
(c) amniotic adults use only metanephric
portion of opisthonephros
Alternate forms of excretion:
1.
mammals, chondrichthyes, few amphibians = urea
2.
reptiles, birds = uric acid
3.
fish, amphibians = ammonia
Other osmoregulatory
organs:
1. sweat glands -- secretion of NaCl and H2O for evaporative cooling
2. liver -- regulation of blood glucose levels,
toxicant removal, and conversion of ammonia to urea (amniotes only).
Excretory systems are
closely aligned with reproductive systems – all vertebrates have
separate structures producing stuff, but......
(a) nonmammalian vertebrates all have common urogenital opening
(cloaca)
(b) nonprimate mammals have separate opening for digestive and
urogenital products
(c) female primates w/
separate openings for digestive, excretory, & gonads.
Mechanisms of sex
determination:
1. chromosomal
sex – a gene on one chromosome initiates gonadal
development for particular gender.
2. environmental sex
determination – temperature, water potential, or other extrinsic factor
influences sex.
The pathway of sperm
(mammalian).
1. From the seminiferous tubules in the testis where they are formed,
sperm travel to the epididymis and vas deferens where
they are stored.
2. During sexual
arousal, muscles surrounding the epididymis, vas
deferens, and urethra contract to eject sperm from the penis.
3. The ejaculated
semen is actually the sperm combined with secretions from three other glands
along the vas deferens, the seminal vesicle, the bulbourethral
gland, and the prostate gland.
These secretions provide nutrients for the sperm and neutralize the
acidity of the female vagina.
The pathway of the
egg.
1. When mature, the
egg is released from a follicle w/in an ovary that is suspended in the body
cavity.
2. The egg is swept
into a fallopian tube where fertilization usually occurs.
3. If the egg is
fertilized, the zygote passes into the uterus where it implants as an embryo
into the endometrium that will form the
placenta. The suitability of the endometrium as an environment to receive the egg is
regulated by hormones from the follicle.
Modes of reproduction:
1. oviparity –
egg-laying
2. ovoviviparity –retaining a
shell-less egg without providing additional nutrients to developing embryo
3. viviparous - providing nutrients to
embryo via placenta
Anatomy of a nerve
cell:
1. cell body --
contains most organelles, serves as integrating center.
2. axon -- long, thin
portion of cell that transmits AP along length of cell.
3. dendrites --
branched portions of cells that respond to stimuli and conduct AP to cell body.
4. synapse -- space
between adjacent neurons across which AP is transmitted via use of chemical
neurotransmitter.
Nerve cells function
to:
1. receive stimuli
from environment (external, internal, other neurons).
2. integrate info.
from stimuli and produce appropriate response.
3. conduct action
potential (AP, signal) along length of cell.
4. transmit AP to
neighboring cell.
The nervous system is
divided into 2 portions:
1) central nervous
system = brain + spinal cord
2) peripheral nervous
system = non-CNS neurons enervating muscle, glands and sensory organs; the PNS
is subdivided into.......
a) sensory division
– detecting stimuli
b) motor division
– responding to stimuli; responses fall into 2 categories
i)
somatic – voluntary responses (conscious control)
ii) autonomic –
involuntary responses that stimulate or suppress activity.
Brain structure &
function
A. Prosencephalon
(forebrain)
1. telencephalon
(cerebrum + olfactory bulb) -- sensory & higher mental function (e.g., intellect, communication, memory).
2. diencephalon (thalamus + hypothalamus +
pituitary) -- homeostasis, endocrine regulation, emotion.
B. Mesencephalon
(midbrain) -- filters & relays sensory info. from all body regions.
C. Rhombencephalon
(hindbrain)
1. metencephalon
(cerebellum + pons) -- coordination & respiratory rate
2. myelencephalon
(medulla oblongata) -- autonomic control of respiration, circulation,
swallowing.
The Senses
A. Chemoreception (smell & taste)
1. olfactory receptors
in nasal passage, sensitive to airborne molecules.
2. taste buds on tongue, sensitive to waterborne
molecules.
B. Mechanoreception (movement)
1. specialized nerve
endings in skin, sensitive to vibration.
2. free nerve endings
in muscles, sensitive to stretching (e.g.,
in bladder, stomach).
3. hair cells in inner
ear, sensitive to vibration or fluid movement; pathway of sound: auditory canal
-> eardrum -> hammer -> anvil -> stirrup -> oval window ->
cochlea -> hair cells on organ of Corti.
C. Photoreception (wavelengths of light)
1. The pathway of light: cornea - aqueous
humor, iris (the opening of which is the pupil), lens (protein, focuses light),
vitreous humor, retina which is composed of two types of photoreceptive
neurons:
a. rods -- greater #, more sensitive,
used for seeing in low light.
b. cones -- lesser #, sensitive to
different wavelengths of light, used for seeing color.
2. Infrared wavelengths detected by pit
organ in Crotalinae.
D. Thermoreception -- the sense of
temperature change, can accommodate.
E. Pain reception -- regardless of the
stimulus, our sense of pain is relatively unchanged because the nerve cell type
is the same throughout the body.
2 types of endocrine
action:
1. water-soluble
hormones bind to IMP receptor on cell surface to trigger rapid responses via
secondary messengers w/in cells (e.g.,
epinephrine)
2. lipid-soluble
hormones pass through cell membrane and nuclear envelope, then binding to
protein receptors that activate DNA expression (e.g., steroids like testosterone, estradiol).
Important endocrine
glands:
1. hypothalamus (base
of brain) secretes hormones that regulate endocrine function of pituitary
gland.
2. pituitary gland
(base of brain) secrete hormones that regulate homeostasis, endocrine function
of adrenal glands and gonads, milk production and secretion in mammary glands. E.g., ADH, prolactin,
FSH
3. thyroid &
parathyroid (neck region) secrete hormones that regulate metabolic and
developmental rate, and calcium uptake for bone growth.
4. pancreas (along
anterior small intestine) secretes hormones that regulate blood sugar levels. E.g., insulin, glucagon.
4. adrenal glands (on
top of kidneys) secrete hormones that regulate metabolic rate. E.g., epinephrine.
5. ovaries secrete hormones that regulate development
of 1¡ and 2¡ sex characteristics in females. E.g., estradiol, progesterone.
6. testes secrete
hormones that regulate development of 1¡ and 2¡ sex characteristics in males. E.g., testosterone.
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Functioning
in an Aquatic Realm
1. Gills use countercurrent exchange to
perform a dual function:
a) respiration –
blood flows across gill filaments in direction opposite to water flow such that
gas exchange rate is maximized; pump or ram ventilation of buccal
chamber; some fish are obligate air-breathers thru gut evaginations.
b) regulating ion
balance –actively transport of NH4, Na+, Ca+2
across gill lining depending on whether organism lives in salt or fresh water.
2. Locomotion:
a) types of lateral
undulation –
(i)
anguiliform: flexion of more than half a sinusoidal
wavelength
(ii) carangiform: flexion of caudal region of body
(iii) ostraciiform: flexion of tail fin only (body is not
flexible)
b) overcoming gravity
–
(i)
positive attack of pectoral fins in water column during forward motion
(ii) swim bladders may
serve dual purpose of gas exchange & buoyancy
(iii) static lift
enabled by low density lipids
c) overcoming drag in
the water –
(i)
decrease body length = decreased surface area for viscous drag
(ii) decrease body
surface irregularities = decreased viscous drag
(iii) decrease % body
length that flexes = decreased inertial drag
(iv) increase aspect
ratio = decreased inertial drag (& burst speed)
3. Sensory perception:
a) photoreception
– spherical lens moved toward/away from retina to focus
b) chemoreception (1¡
mouth) is relatively sensitive
c) mechanoreception
– specialized lateral line system of neuromasts
provide info about orientation, water current, motion, pressure.
d) electroreception
– modified muscle cells, electrocytes, synchronously
generate net positive unidirectional current (² 600 v) for orientation,
communication, or predation.
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END OF MATERIAL FOR 1ST EXAMINATION
Class
Cyclostomata – life
with a tripartite brain
Advantages over uro- & cephalo- chordates:
1. true cephalization
and a tripartite brain housed w/in cranium
2. increased
complexity of sensory organs
3. pharyngeal
musculature for increased H20 velocity (incr. respiration).
4. bone for incr.
sensory and activity levels
Characteristics of
Class that distinguish from other vertebrates:
1. jaws absent
2. two sets of paired
appendages absent.
Order Myxinoidea
(hagfish)
1. > 40 sp., w/ global distribution
2. vertebrae absent
3.
exclusively marine, mostly benthic in habit
4.
single nasal opening, mouth surrounded by 6 tentacles and housing a
tongue covered in keratinized "teeth;" feed on inverts and dead vert.
viscera
5.
multiple subQ glands secrete mucous as antipredator defense.
6. isoosmotic w/ seawater; multiple blood sinuses, ea. w/ its
own "heart."
Order Petromyzontoidea (lampreys)
1.
41 sp., w/ global distribution (fresh or salt H20 except
tropics & polar seas)
2.
anadromous – ascend streams to spawn, mature in oceans.
3.
funnel-shaped mouth lined with keratinized "teeth" and
containing protrusible tongue w/ similar covering; oral gland secretes
anti-coagulant.
4.
7 pairs of gills for respiration and assist kidneys w/ osmoregulation; single heart with autonomic enervation.
5.
Following construction of canal between Lakes Ontario and Erie, colonized
all of upper Great Lakes and impacted commercial fishery (1¡ trout).
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Gnathostomata
– life with jaws
Advantages over
Cyclostomata:
1. jaws present
2. two sets of paired
appendages.
3. development of
postorbital process (segregates musculature for jaws & eyes)
4. distinct ducts
linking gonads to excretory duct(s).
5. spleen present
6. lateral line system
along trunk w/ specialized scales.
Improved gill
ventilation conferred improved mobility & predation.
a. jaws arose from 1st
pharyngeal arch (mandibular) – helped suck prey in
b. enlargement of
adductor mandibularis muscle allowed holding onto
prey with jaws closed whilst water was forced over gills (in pharynx).
Features for improved
mobility:
1. more complete
vertebrae w/ attached ribs
2. distinction of
epaxial and hypaxial musculature
3. myelinated
neurons
4. conus
arteriosus receives blood from ventricle
5. fins that
controlled guiding body in 3-D environment via keratinized or bony fin rays
from pectoral and pelvic girdles.
Class Chondrichthyes
– distinguishing characteristics from other vertebrates:
1. cartilaginous
skeleton
2. intercalary plates
along spinal column protect nervous & circulatory system
3. fused halves of
pectoral girdle to aid in jaw protrusion
4. swim bladder absent
(but liver oil provides some buoyancy
5. ampullae of Lorenzini are mucous-filled tubes containing sensory cells,
and concentrated in snout region for electromagnetic perception of
surroundings/prey.
Groupings of
Chondrichthyes:
1. Subclass Elasmobranchii –
a) pleurotremate =
gills on the sides (typical shark body form, 360 spp.); mostly active
carnivores, but a few passive planktivores.
b) hypotremate = gills
underneath (typical ray body form, 460 spp.); mostly benthic detritovores, a few pelagic passive planktivores;
a few skates can localize electric field to stun prey.
2. Subclass Holocephali – chimeras w/ only 1 gill opening on each
side of head; 30 spp.; mostly demersal, some with a
venomous dorsal spine.
Success (sp. diversity
and relatively large body size) enabled by variable repro. modes – all w/
internal fertilization:
1. females w/ nidimental glands that secrete proteinaceous
"shell" around egg
2. ovoviviparity in
many spp., but all nourishment from yolk (lecithotrophy)
3. matrotrophic
viviparity (mother provisions, but no circulatory exchange).
4. placentotrophic
viviparity (nourishment exchange via vascular yolk)
––––––
Class
Osteichthyes – life
with a bony skeleton
Advantages over
Chondrichthyes:
1. skeleton of endochondral bone (replaces cartilage in juveniles)
2. webbing between
bony (dermal) fin rays.
3. operculum covering
gill arches
4. enlarged,
protrusible maxillae (allowed gape-'n'-suck feeding)
5. reduced dermal
armor
6. swim bladder as evagination from gut
Subclass Actinopterygii
– ray-finned fishes, Å 24,000 sp.
1. bony rays (more or
less parallel) supporting fin membrane, increased fin flexibility and therefore
mobility
2. hypural bones from
up-turned caudal vertebrae into tail formed homocercal tail that increased
mobility
3. flexible skull
& cheek increased orobranchial chamber volume,
thus increased predatory & respiratory ability
(a) Superorder Acipenseriformes – sturgeons & paddlefish;
cartilaginous skeleton, freshwater or anadromous, desirable for caviar.
(b) Superorder Neopterygii – bowfins, gars, all other bony fish;
many have Weberian apparatus (combined use of swim
bladder and inner ear to increase sensitivity to vibration)
Subclass Sarcopterygii
– lobe-finned fishes
1. fleshy fins with
bony central axis
2. two dorsal fins
3. enlarged head
musculature
(a) Superorder Actinistii – Latimeria (coelacanth, a "living fossil"); marine,
carnivorous w/ internal fertilization.
(b) Superorder Dipnoi – lungfish; freshwater w/ poor gill function,
so evaginations from gut (former swim bladder) modified
into single or pair lungs, aestivate to escape drought conditions
When swimming, species
from both of these groups move their pectoral and pelvic fins in a manner
similar to tetrapod limb movement, suggesting that this Subclass contained the
species that gave rise to all tetrapods.
––––––
Fun-filled
facets featuring fish
The largest group of
fish is w/in Actinopterygii are in Order Perciformes
(e.g., perch, bass, snapper, tuna,
cichlid, dolphin); these show a wide variety of life history strategies.
1. Marine:
(a) repro. –
most spp. w/ ext. fertilizat'n and pelagic eggs & larvae. Why?
i)
removal of larval stage from some predator sp.
ii) predator satiation
iii) rapid, wide
dispersal
iv) increased nutrient
access in highly-productive pelagic zone
v) reduced spp.
vulnerability to environmental perturbation
Exceptions:
i)
grunion (Leuresthes):
females deposit eggs in sand where they are fertilized.
ii) anglerfish (Liophryne): males
feed only during larval stages & are then parasitic on female during/following sexual maturation
iii) seahorse (Hippocampus): male protects eggs/larvae
in "pouch"
iv) blue wrasse:
sequential hermaphroditism from female to male
v) coelacanth (Latimeria):
internal fertilization w/ ovoviviparity
(b) biogeography
– decreased light penetration @ depth = decreased photosynthesis =
decreased food availability = decreased spp. richness
i)
epipelagic fish = those in the photic
zone
ii) mesopelagic fish
often migrate to photic zone to feed but then retreat
to depth to lower predation risk and metabolism
iii) bathypelagic fish
(> 1000 m deep) rely either on detritus from upper zones or sympatric
species for food; eyes, mouth, & teeth rel. larger b/c food is scarce, some
use symbiotic bioluminescent lures.
2. Freshwater:
(a) repro. –most
spp. produce rel. few eggs & provide parental care @ nest site; b/c
swift-moving water can displace larvae from ideal habitat conditions.
Exceptions: i) pupfish (Cyprinodon): satellite male w/ female
color sneaks between territorial male and receptive female to fertilize eggs.
ii) bluegill (Lepomis): males
establish colonial nests to reduce predation risk
iii) cichlid (Oreochromis):
some spp. are mouth-brooders; many spp. w/ parents secreting nutritious mucous
on skin, eaten by larvae.
3. Ontogeny:
Otoliths
w/in inner ear, used for orintation, are mineralized
records of daily environmental conditions that effect fish growth. Can be used to popln
biol.
4. Conservation:
Fisheries management
is difficult b/c of unpredictable environment where eggs & larvae develop
(esp. marine). Fisheries typically
in cool waters w/ higher O2 content (= higher productivity), but
areas are being overfished w/out recruitment. Threats also from pollution, habitat destruction, siltation.
––––––
Tetrapoda
– the fin-to-limb transition
Why give up aquatic
life?
1. increased food availability
2. increased oxygen availability (reqÕd
evolution of cutaneous respiratÕn)
3. decreased predation pressure
4. stable climate – recall biogeographical history: ~ 180 mya
continents rejoined (enabling radiation across all available land) and mtns. formed (generating isolating barriers).
How does a land animal
evolve in water?
á
flexible lobed fins facilitated prey
capture for ambush predators.
á
If living in water w/ low [O2],
swim bladder that maintained buoyancy could also be used as a means of
obtaining O2 (gulping air)
Who got sick of the
water first?
Ancestral group to all tetrapods is the
Sarcopterygii (Òflesh-finnedÓ fish)
: lobed fins
: dorsally oriented
eyes on elongate head
: ventrally-projecting
ribs
Specifically, Ichthyostega and Acanthostega
: digits in their fins
: partially-ossified
articulating vertebral centra
: enamel on teeth
: linked charÕs to
fish (opercular bone, caudal fin, lateral line)
1st 200 mya of tetrapod radiation was vast, the stem group referred
to as the Labyrinthodonts (b/c of infoldings
of enamel on teeth). This group
radiated in two directions –
: Reptilomorpha
(further discussion later)
: Batrachomorpha,
with a more aquatic life style, gave rise to modern groups of amphibians.
In addition to
radiation onto land, diversity of early amphibians included several life styles
that returned to fully-aquatic existence –
: dorso-ventrally
flattened body
: retention of
external gills (paedomorphic)
: elongate, flat snout
seen in amphibious fish-eaters
––––––
Amphibia
–– Life on land (sort of)
Class Amphibia Å 4,600
species in three major groups; shared characteristics:
á
all carnivorous
á
anamniotic – risk of dessication limits repro.
á
3-chambered heart, with cutaneous artery
off aorta
á
scaleless
skin with common components
á
stratum corneum – outer-most layer
which is dead, & occasionally shed
á
mucous glands secrete mucopolysaccharides
to facilitate respiration, temperature regulation, water balance, locomotion,
& defense (e.g., some spp.
aestivate during dry periods by shedding several skin layers and then coating
the inside of the ÒcocoonÓ with mucous)
á
granular glands – secrete alkaloid
poison in defence (lower density)
á
chromatophores
– pigment cells to alter skin color
Order Caudata (salamanders) Å 400
species in 9 Familes
General
characteristics:
b) elongate
bodies, usu. w/ 4 limbs, always w/ tail
c) mostly
small size (< 12 cm SVL, < 10 g), except some Cryptobranchidae
Order Anura (frogs) Å 4100 species in
18 Families
General
characteristics:
–
all spp. have limbs, but lack tails
(except in 1 sp.)
–
modified skeletal characteristics for
saltation (jumping)
á
elongate hind limbs w/ fused tibia and
fibula
á
elongate illia
of pelvic girdle
á
fused posterior vertebrae into urostyle
á
ribs reduced or absent
á
flexible pectoral girdle (cartilagenous sternum) to cushions landing
Order Gymnophiona Å 100 species in 5 Familes; pan-tropical distribution
General
Characteristics:
á
adaptations for fossorial/benthic
life
1. Limbless,
elongate, externally-segmented body.
2. Vestigial
eyes and left lung
3. Dermal
scales usu. present (co-ossification of skin to bone).
4. Specialized
tentacle for chemoreception between nostrils and eyes.
á
Reproductive modes
a) <
50% oviparous, with parental care
of rel. large clutch
b) 50
% viviparous with clutch size < 10.
––––––
When
is a frog not a frog? – Amphibian
diversity
An evolutionary look
at the diversity of natural history traits
b) repro.
mode – primitive = ext. fert.; derived = int. fert. involving complex courtship behavior called amplexus
(male grasping behind forelimbs of female) & male deposition of spermatophore
that is collected by female
c) breeding
habitat – primitive = lentic water; derived = lotic
water
d) repro.
output – primitive = many small eggs; derived = few large eggs w/
guarding behavior, sometimes on land (viviparity in only 1 Genus)
e) feeding
mechanism – primitive = suction feeding in aquatic spp.; derived =
projectile tongue in terrestrial spp. (esp. Plethodontidae: fleshy tongue
protruded via squeezing of protractors around hyoid bone and simultaneous
contraction of retractor muscle.
f) paedomorphosis
– retention of jr. charÕs. into adulthood, esp. common in primitive
families
g) elongation
and limb & lung loss – elongation always precedes loss;
lung(s) lost to decrease frictional dragtypically
seen in fully-aquatic spp. in well-aerated streams
Order Anura
á
Mode of locomotion –
á
Saltation enabled by 5 folding parts:
pelvic girdle, femur, tibiofibula, tarsal bones, phalanges. Muscles on these parts are larger
closest to body, and are not antagonistic. Motion is symmetrical and mid-jump body posture is
aerodynamic. Intraspp. variation due to physical
condition, temp. Smaller spp. also
jump relatively farther than large spp.; but ability also depends on
natural history – burrowing < aquatic < arboreal < grass/reed
frogs (e.g., Ranidae).
á
Swimming facilitated by synchronous
movement of hind limbs, dorsoventrally-flattened
hydrodynamic bodybody, mucous coat.
á
Arboreal movement facilitated by expanded
sticky toe pads, moist skin
á
Fossorial movement facilitated by short
strong hind limbs w/ ÒspadesÓ on posterior margin of feet.
á
Mode of reproduction –
á
Resonating chamber for voice formed as 2¡
sex char.; calls are specific to spp. and can be affected by temp.
á
Male-male combat common, winner mates
while in amplexus
á
Primitive = lay-ÔnÕ-leave in water,
typically attached to substrate; derived = laying out of water, direct
development, or parental care.
á
Mode of feeding –
á
1¡ insectivorous
á
Obtain prey by tongue-flipping while
lunging at prey; several rows of teeth to secure captured prey.
a) Spin-&-shear
feeding on invert. prey
b) If
viviparous, 1st 3dr of development fueled by yolk,
remaining period by Òuterine milkÓ secreted in female oviduct; when born, young
may be up to 60% of femaleÕs body length (she must feed during gestation).
––––––
Interesting form &
function
á
Salamander respiration : Cryptobranchidae – retain gill slits, but use lungs; Proteidae & Sirenidae –
retain external gills and use lungs; Plethodontidae – lungless
á
Salamander appearance : Ambystomatidae – paedomorphosis
in some spp., or in some populations w/in spp.; Plethodontidae – cave
dwelling in some spp. has led to eye and pigment reduction/loss.
á
Frog appearance : tailed frog w/ internal
fertilization; spade-foot toads w/ enlarged tubercle on hind feet to burrow
into soil; flying frogs w/ large webbed feet rel. to body size; Goliath frog up
to 3 ft. SVL
Interesting
reproductive strategies
á
Pacific giant salamander w/ internal fert., individually-laid eggs that take up to 9 moÕs. to
hatch, & aquatic larval stage of up to 6 yrs.
á
Midwife toad males wrap strands of
fertilized eggs around waist, carry them for weeks, & deposit them into
water when ready to hatch into larvae; Suriname toad pairs swim in loops while
in amplexus such that fertilized egg rolls onto back of female where it embeds
under layer of skin for direct development; DarwinÕs frog males guard eggs by
placing them in vocal sac; max. clutch size in Ranidae
= 47,840 eggs (bullfrog)
Interesting behaviors
á
Several frog spp. w/ satellite males that
do not call around breeding ponds, but intercept females as they arrive
(survivorship advantage in areas w/ high predation?)
Interesting
anti-predatory adaptations
á
Live where you cannot be found (e.g., fossorial caecilians, cave
salamander)
á
Cryptic coloration and color change (e.g., gray treefrog)
á
Rapid change of habitat
(land–air–water) in frogs
á
Aposematic (warning) coloration in many
spp. confers presence of toxins.
á
†nken
reflex in salamanders and frogs exposes contrast-colored ventral surface to
predators
á
Poison-dart frogs w/ derived skin toxins
(alkaloids) that are lethal
––––––
END OF MATERIAL for 2nd
midterm exam
Reptilia
– Life with an amniotic egg
Class
Reptilia Å 6,000 spp. in 4 major groups; all land masses except polar.
Advantages
over the amphibians:
á
Amniotic egg with a calcareous or
leathery shell that prevented desiccation whilst also used as a respiratory
surface (amnion surrounded embryo in fluid, allantois stored embryoÕs metabolic
waste).
á
Scaly, water-tight skin preventing
desiccation
á
Rotation of limbs to ventral side of body
á
Increased jaw mechanism to handle
larger/harder insect prey
Å
170 Families of reptiles have gone extinct; so, why were they dominant?
d) Highly
developed sensory systems
e) Some
degree of sociality, aggregative behaviors
f) Enhanced
thermoregulatory ability (some evidence of homeothermy in dinosaurs, but
couldnÕt survive glaciations)
Primitive members of Amniota
had only the orbit and naris openings in their
skulls. Subsequent radiation
within this clade produced two major groups, each
having a distinct suite of traits, where skull morphology diverged.
Synapsida
– one additional hole posterior to the orbit. This led to Mammalia (discussed
later).
Sauropsida
– other skull morphologies, ranging from none to two holes posterior to
the orbit.
Subclass Anapsida,
Order Testudines (turtles) Å 240 spp. in 13 Families
General characteristics:
á Oviparous,
laying eggs on land
á 2
parts of bony shell, carapace & plastron, to which vertebrae are fused
á teeth
absent, replaced by keratinized beak
2 groups : pleurodires
= side-necked turtles; cryptodires = ÒhiddenÓ-necked
Extant diapsid skull
morphologies
Subclass
Archosauria, Order Crocodylia Å 22 species in 3 Families, 1¡ tropical
General
characteristics:
– Oviparous,
constructing terrestrial nests for eggs
– Thecodont
teeth, well-developed palate
– Laterally-compressed
tail
– 4-chambered
heart
– 1st
evidence of neocortex tissue in brain, leads to complex behavior
3
Families:
Alligatoridae
– rel. broad snouts, only upper teeth show when jaws closed.
Crocodylidae
– narrow snouts, 4th lower incisor protrudes when jaws closed.
Gavialidae
– rel. long narrow snouts, 4th lower incisor protrudesÉ.
Subclass
Lepidosauria (all diapsid skulls)
A. Order Rhynchocephalia (tuatara), 2 spp.
on New Zealand
á
Oviparous, 13-14 incubation period;
sexually mature @ 20, lives to 50
á
Pineal eye (unlensed,
dorsomedially placed)
á
Acrodont teeth w/ 4 upper jaw rows, 1¡
insectivorous
á
Order Squamata – all having
determinate growth, hemipenes
Suborder
Sauria (lizards) Å 3,760 spp. in 16 Families, most abundant reptile
á
Global distribution except for polar
regions
á
Eyelids and external ear present
á
Paired kidneys placed posteriorly
Suborder
Amphisbaenia Å 140 spp. in 4 Families, pantropical distribution
Fossorial
adaptations include:
5. limblessness,
but w/ vestigial girdles
6. elongate
body w/ annuli to facilitate bi-directional movement, only 1 lung
7. external
ears absent
8. skull
entirely compact bone, w/ flattened snout
Suborder
Serpentes (snakes) Å 2,400 spp. in 11 Families, global distribution
General
characteristics:
c) Eyelids,
external ears, tympanum, eustacian tubes absent
d) Girdles
extremely vestigial or absent, sternum absent
e) Urinary
bladder absent, 1 lung, paired organ displacement or partial loss.
f) Mandibular
symphysis absent, skull bones loosely connected
Why
go w/out limbs, and what characters are assoc. w/ change?
á
Having a low-profile, lizards had hard
time getting through vegetation or into holes to chase prey/escape predators;
eventually folded limbs against body and used lateral undulation to propel
bodies (similar flexion in fish).
á
Loss of body demarcation
á
Decreased body diameter, but more
elongate
á
Cranial kinesis
á
Displacement of paired organs along anterio-posterior axis or loss of 1
––––––
Reptiles know theyÕre ÒcoolÓ
–– reptilian diversity
Turtle
morphology types
á
Tortoises are dome-shelled, terrestrial,
herbivores
á
Pond turtles have flatter shells, &
typically undergo ontogenetic shift in diet
á
Fully-aquatic turtles have flat &/or
reduced shells, usu. carnivorous
á
Sea turtles have modified limbs, serving
as paddles, hydrodynamic shells, and no ability to fully retract head.
Tuatara life history & conservation
á
Historically found throughout NZ, now
only on peripheral islands
á
Colonial nesters assoc. w/ seabirds
(indirect source of prey)
á
Hemipenes absent, intromission via
Òcloacal kissÓ
á
Lower thermal preferendum than most herps (6 – 16 ¡C)
Evolutionary
trend towards elongation &/or limblessness in squamates
Advantages:
g) Fossorial
movement – less E to small-diameter body into hole
h) Crevice
access – easier access to prey, escape from predators
i) Permits
new types of locomotion (see below)
Disadvantage:
smaller spp. cannot feed on large prey mass
Solutions:
eat more often, eat big items, or eat chunks of prey.
Squamate
feeding ecology
Specialized
prey detection mechanisms
g) Stereoscopic
vision – chamaeleons only
h) Loral
pits to detect infrared wavelengths (boid and viperid
snakes)
i) Vomeronasal
organ sensitive to chemosensory cues (most reptiles)
Tongue
types
á
Fleshy blob – similar to human
tongue, 1¡ for food manipulation
á
2-part tongue – ant. for
chemoreception, post. for food manipulation
á
snake tongue – carries chemical
cues to vomeronasal organ
á
chamaeleon
tongue – modified fleshy blob, projection by muscle around modified hyoid
bone
Subduing prey (derived
in Serpentes)
1. Constriction – Boidae, Colubridae
2. Envenomation – 2 lizard spp., colubridae, elapidae, viperid
snakes
á
Aglyphous – same-sized teeth, no
venom, all teeth used to grasp prey
á
Opisthoglyphous – most-posterior
tooth enlarged, attached to venom gland
á
Proteroglyphous – shorter maxilla,
most- anterior tooth enlarged & attached venom gland usu. producing
neurotoxin
á
Solenoglyphous – greatly reduces
maxilla w/ only one channelized tooth (true fang) attached to venom gland usu.
producing hemotoxin
Cranial kinesis
(derived in Serpentes)
á
Loose attachment of teeth to jaw bones
á
Mandibular
symphysis absent – unilateral movement of
jaw halves
á
Streptostylic
quadrate bone that articulates laterally, ant.-posteriorly,
dorso-ventrally
Methods
of limbless locomotion in squamates
á
Lateral undulation – S-shaped
flexion w/ force applied against substrate
á
Concertina locomotion – alternation
of anchoring and pushing/pulling body sections forward, common in tight
spaces/burrowers
á
Rectilinear locomotion – sequential
contraction of abdominal muscles articulating between indiv.
ribs and ventral scales, pulling body forward, common in heavy-bodied snakes
á
Sidewinding
– 2 points of contact with soft substrate, b/c middle of body is thrown
forward in loop @ oblique angle to direction of movement.
––––
Rapturous reports regarding reptiles
Morphological
variation
á
Scale modification for defense (Phrynosoma),
communication (Anolis).
á
Caudal storage of fat in spp. of xeric
habitats (Heloderma)
á
Elongate ribs for defense (Naja) or flight (Draco)
á
Lateral or dorsoventral
compression in aquatic spp. (crocs., seasnakes)
á
Lateral compression in arboreal spp. (Oxybelis, chamaeleons)
Physiological
performance
á
Nasal or orbit gland to facilitate osmoregulation (seaturtles, seasnakes, etc.)
á
Cardiac shunts facilitate
thermoregulation & diving (marine iguanas, sea turtles, crocs.)
á
Cloacal respiration facilitates
respiration in aquatic turtles (Apalone)
Variation
in reproduction (all w/ internal fertilization)
Hemipenes present in all
but Rhynchocephalia (1 in turtles/crocs., 2 in squamates); spp. i.d. often
facilitated by hemipenes ornamentation.
a)
Mate attraction/communication
á
visual = dewlaps in Anolis, head-bobbing in Iguana
á
chemical = femoral pores in Sceloporus,
pheromones in Thamnophis
b)
gestation modes
á
Sexual repro. via oviparity (most spp.), ovoviviparity (Nerodia),
and viviparity (Thamnophis).
á
Asexual repro. via parthenogenesis
(diploid eggs) in 3 lizard families
c)
parental care (absent in Testudines; universal in Crocodylia)
á
Egg attendance (Eumeces, Naja)
á
shivering thermogenesis
for incubation (Python)
á
post-partum attentiveness (Crotalus)
Squamate anti-predatory
mechanisms
á
Cryptic, disruptive, or aposematic coloration, or mimicry
á
Escape – good runner w/ larger hind
limbs, some bipedalism in lizards
á
Flight – gliding via rib extention of patagia (skin flaps)
á
Biting/venom (2¡ [derived] function of
the latter)
á
Tail use: (a) whip-like or spiny tails
lashed at predator; (b) warning or mimicry in snakes; or, (c) autotomy in lizards, tail fractured along plane between
vertebrae, replaced w/ cartilage
á
Fluid ejection in Colubridae,
Phrynosoma
––––––
Throwing out the thermometers – high-energy life
Endothermy has
associatedÉ
Benefits:
¥ allows maintenance of high body tempÕs. in absence of sunÕs heat
j) Allows
year-round activity
k) Allows
activity in areas devoid of ectotherms (predators)
Costs:
¥ energetically expensive w/ increased metabolic rates
h) Increased
risk assoc. w/ needing to eat more.
i) Increased
osmoregulator precision reqÕd
Dealing
with the coldÉ
1. Get out of the freezer (!) –
migration (e.g., whales, birds)
j)
Stimuli = photoperiod, temp. change,
lunar periodicity, food availability
k)
Benefits = greater distribution, stable
food supply, suitable repro.habitat
l)
Costs = energy, risk assoc. w/ movement,
territorial re-establishment
2. adaptive hypothermia – torpor
– lowering metabolic rate either daily or seasonally (hibernation), saves
E and H2O.
3. regulating body temp. [Why not increase
heat production?]
Decreasing
heat loss byÉ.
–
Increasing length &/or density of
outer body cover (feathers, fur)
–
Increase metabolic rate
–
Decrease SA:V ratio (larger &/or more
compact body form)
–
Increasing thickness of insulating fat
(esp. in aquatic spp., blubber)
–
Circulatory shunts away from body surface
–
Countercurrent heat exchange in
circulatory system
Dealing
with the heatÉ.
á
Get out of the desert (!) – avoid
heat byÉ.
c)
Retreating to subterranean burrows or
shaded habitat
d)
Crepuscular or nocturnal activity
á
Diurnal torpor for conserving E
á
relaxation of homeostasis (tolerance
overheating &/or water loss)
á
specializations in hot environments
á
morphology &/or body posturing
á
evaporative cooling (panting, sweating)
á
counter-current circulation
––––––
Aves ––
Life with feathers
Class
Aves Å 9,000 spp. in 27 Orders; common characters:
á
oviparous, scales present – shared
w/ Reptilia
á
endothermic, 4-chambered heart, lg.
cerebellum – shared w/ Mammalia
á
wings (not unique, but not universal in
other Classes)
á
beak in place of teeth (ditto)
á
air sacs as extension of lungs
á
lg. eyes w/ superior accuity
& accommodation unique to Aves
á
feathers (modified ectodermal
scales)
Why
should ÒlizardsÓ fly? 2 competing
hypotheses:
á
bipedal lizard w/ good running speed
developed gliding feathers to get off ground for prey capture.
á
quadriped
arboreal lizard w/ good cerebral vol. leapt from perches and developed gliding
feathers.
Features
assoc. w/ flight (incr. E efficiency & support whilst decr.
mass)
á
decr.
bone #, incr. bone fusion & mineralizatÕn, shift
bone wt. ventrally
á
bone pneumatization
– hollow larger bones w/ structural braces
á
teeth replaced by gizzard in g.i tract
á
lg. orbital fossa
= lg. eyes for incr. visual perception
á
keeled sternum for incr. SA for
attachment of flight muscles
á
Òflow-throughÓ respiratory system
á
feathers (also for communicatÕn,
insulatÕn, protectÕn,
sensory perceptÕn)
Increased
cardiovascular performance:
á
4-chambered heart completely separates O2
& de-O2 blood
á
counter-current circulation around lungs
á
Respiration – inhalation both draws
air in to post. sacs & pushes air from lungs to ant. sacs;
exhalation pushes air from post. sacs to lungs & releases air in
ant. sacs to outside body.
Feather
care
á
Uropygial
gland (@ tail base) secretes oil for waterproofing feathers
á
Molting (progressive or synchronous)
replaces damaged feathers
Some
feather types
á
Contour = basic type for flight &
protection
á
Down = insulatory
á
Bristles = projections around mouth as a
ÒwebÓ to catch insects
á
Powderdown
= on spp. lacking uropygial gland, help to fill out plummage
Flight
mechanism
–
Cambered airfoil shape of wing forces air
moving across wing into less space on top surface, into more space on bottom
surface
–
BernoulliÕs Law: · dynamic & static
pressure = constant
–
So, if dynamic pressure is higher on top
wing surface, then static pressure must be less, generating lift; but, this
force must exceed drag
–
Drag due to surface friction (across)
& induced friction (around)
–
Aspect ratio = wing length : wing width
(^ ratio = lower drag coeff.)
Types
of flight
á
Forward thrust – down stroke pushes
air behind wing, most of lift generated @ distal wing b/c of faster feather
movement.
á
Gliding/soaring – maintaining
altitude &/or direction w/out wing movement, higher aspect ratios, lower
wing loading (e.g., Falconiformes)
á
Hovering – maintaining position b/c
down- up-strokes both generate lift whilst counteracting the otherÕs thrust (e.g., Apodiformes)
Digestive
tract (ant. – post.)
á
Mouth w/ bill (epidermis around bony
core) & esophagus
á
Crop – enlarged sac in grani- & carni-vores for
temp. food storage
á
Stomach – regions for chemical & mechanical (gizzard) breakdown of
food
á
Intestine – length varies w/ spp.Õs diet
á
Cloaca
– secretes uric acid, no intromittent organ
(use Òcloacal kissÓ)
––––
Birds of a feather don't necessarily
flock together –
avian diversity
Territory
– area w/in home range defended from conspp.
Factors
regulating size include:
á
Food abundance
á
Body size; ^ size = ^ territory, esp. in
carnivores
á
# of indivÕs
&/or spp. competing for the same territory
á
season; territories can be smaller when
resource is seasonally-abundant
Communication
mechanisms:
1
Plumage display (e.g., Galliformes)
á
Non-vocal sounds:
Hammering bill against substrate (e.g., Piciformes)
Drumming against substrate (e.g., Galliformes, Anseriformes)
Flight noises (e.g., Columbiformes, Apodiformes)
á
Vocal sounds – types:
Calls are simple, usu. monotonal, used by both sexes yr.-round
Songs are tonally complex, usu. male
performance during breeding season
Song functions:
– territory advertisement/defense
á
attracting females
á
strengthening pair bonding (e.g., duetting
in wrens)
á
stimulating/synchronization of repro.
condition
á
teaching to male offspring
Song development:
– little/no learning; isolation
doesnÕt influence song (e.g. Columbiformes)
á
learning from conspecific
neighbors; some reinforcement reqÕd.
á
learning from adult male; closest bird
influences development
á
learning from mate; ea. learns from
other, reinforcing bond (wrens)
á
heterospecific
learning, song develops beyond 1¡ song (e.g.,
Mimidae)
Mating
systems – aspects of social organization explaining how/when/which males
& females come together for breeding
1. monogamy (92% of spp.); can be
perennial (e.g., geese) or seasonal
2. polygamy; can be harem or serial
a) polygyny = 1
male : >1 female; can be resource-defense or male-dominance
a) polyandry
= >1 male : 1 female (usu. male-only parental care)
3.
promiscuity (6% of spp.); no mate fidelity (e.g.,
woodcock)
Migration
– types:
á
Short-distance; usu. ^ lat. or alt. for
breeding (e.g., some sparrows/juncos)
á
Long-distance, along N-S axis (75% of Neartic passerine spp.)
á
E-W axis; from interior to coastal
regions (e.g., shorebirds)
á
Wet-dry; following wet seasons to forage
on seeds released following rains
á
Loop; usu. following prevailing winds or
differential prey abundance
á
Reverse; usu. in seabirds b/c cooler
water is more productive
á
Habitat; forest interior birds move to
marshlands for food resource
Cues:
(restlessness response by bird referred to as Zugunruhe)
á
Topographic; following river beds, coastlines,
etc.
á
Stellar; orientation to stars based on
seasonal rotation around fixed point
á
Sun; proximate cue = photoperiod
á
Geomagnetism; innate compass detects
EarthÕs magnetic field
––––––
Breath-taking bits 'bout birds
The
Flying Game – the losers (flight loss derived)
á
Stealthy birds in dense habitats (e.g., rails, kiwi)
á
Large birds in open, sparse habitats (e.g., ratites: ostrich, emu, rhea)
á
Birds that ÒflyÓ through water (e.g., penguins)
á
the winners
á
greatest speed in Falconiformes
(Peregrine Falcon stoops @ 300 km¥hr=1)
á
greatest manÏuverability
in Apodiformes (hummingbird flies backwards)
á
greatest stealth in Strigiformes
(barn owl)
á
greatest distance in Charadriiformes
(artic tern migrates 36,000 km yr-1)
á
greatest altitude in Falconiformes
(griffon @ 11.2 km)
Specialized
feeding morphology:
á
Pouches in Pelicaniformes
used as dip nets
á
Combs in bill of flamingos for sifting
through mud
á
Serrated bills in fish-eating mergansers
(Anseriformes)
á
Crossbills extract seeds from between
pinecone scales
á
Skimmers w/ longer lower mandible forage
in water whilst flying above it
á
Loggerhead shrike impales prey on plant
thorns for temporary storage
Courtship/Nesting
strategies:
á
Bowerbirds clear area on forest floor and
ornament w/ conspicuous objects
á
Galliformes
and Birds-of-Paradise w/ elaborate feathers & display
á
Nest parasites; cowbirds and cuckoos lay
eggs in nests of other spp.
á
Altruism in woodpeckers, jays (care of
siblings @ repro. maturity)
á
Òprostitution behaviorÓ in hummingbirds
(resource-defense polygyny)
á
Colonial nesting (usu. monogamous spp.)
– advantages:
^ predator vigilance and anti-predator
response
predator satiation w/out extinction
cooperative efforts to exploit aperiodic
resource
á
disadvantages:
^ competition (for food and nest sites)
predators key on colonial sites
resource over-exploitation
––––––
END
OF MATERIAL FOR 3rd midterm exam
Mammals ––
Life with milk production
Class
Mammalia Å 4,400 spp. w/ global distribution. Unique characteristics:
á
4-chambered heart w/ tricuspid valve
separating chambers on right side
á
anucleate
biconcave erythrocytes
á
occipital condyles
supporting skull; largest rel. brain size/complexity
á
complete 2¡ palate w/ 2 ÒsealsÓ
á
heterodont,
diphyodont dentition
á
endothermic w/ insulation of hair
á
mammary and sebaceous glands
Evolutionary
novelties associated with incr. metabolic demand/provision (Diapsida
ˆ Synapsida ˆ
Therapsida ˆ
Mammalia)
á
greater cranial muscle mass, esp. around zygomatic arch
á
heterodont
dentition w/ tooth specialization
á
2¡ hard palate (eat/breathe
simultaneously)
á
ventral centering of limbs enhanced locomotory performance
á
shorter tail and reduction of lumbar
vertebrae
á
calcaneal
heal provides stronger lever for gastrocnemius muscle
3
major groups w/in Class:
Subclass
Prototheria – 1 Order, 3 spp.; Australia, New
Guinea
á
Oviparous (shell gland in oviduct)
á
Females incubate eggs; mammary glands
lack nipples but young suckle from tufts of ventral hair
á
Males lack seminal vesicles and prostate
gland; penis everted from ventral wall of cloaca (common urogenital
opening).
E.g., duckbilled
platypus, echidna
Subclass
Theria –non-oviparous mammals
Infraclass
Metatheria – 1 Order, Å 200 spp.; most in
Southern hemisphere
á
Choriovitelline
placenta (formed from chorion & yolk sac membrances)
á
Viviparous, all spp. w/ altricial young
á
Females have marsupium
in which young complete development
E.g., koala,
kangaroo, tasmanian devil, opossum
Infraclass
Eutheria – 20 Orders, global distribution
á
Chorioallantoic
placenta (formed from chorion & allantois membranes)
á
Viviparous, many species w/ precocial young
á
Largest cerebrum ˆ reasoning
& cognitive processing.
Specializations
w/in Class –
1. Hair/fur is dermal outgrowth projecting
through epidermis, 2x as strong as bone per unit size (i.e., very elastic); 2 types
á
underfur
– thick, short, 1¡ for insulation
á
guard hair – long, stiff, 1¡ for
protection
2. Skin glands
á
mammary glands – found in all
females (& most males) where functional development from ventral thoracic
epidermis is homonally regulated (oxytocin,
growth hormone); secreted milk high in albumin, lactose, fat.
á
sweat glands – epidermal, 1¡ for
thermoregulation, but also ion balance
á
sebaceous glands – demal, @ base of hair follicle, secrete waxy oil to moisten
hair/fur
á
lacrimal
gland – secretes isoosmotic fluid to
moisten/clean eye
á
scent gland (musk) – anal gland for
communication, defense, territoriality, & sexual attraction
Alternate
functions of hair/fur
á
Sensory perception – vibrissae on canids, felids
á
Locomotion – rudder width in flying
squirrels
á
Communication – aposematic
(skunks), aggression (canids, felids), sexual
dimorphism (primates)
á
Specialized function – bristles in suids, quills in porcupine
Loss
of all but a few hairs is derived for various functions (e.g., reducing frictional drag in Cetacea,
manatees, naked mole-rats).
What can you do with 12 cranial nerves? – mammalian diversity
Body
ornamentations
á
Giraffe horns – unbranched
permanent bone covered w/ skin and fur
á
Horns – bony core covered by
keratinized epidermis, permanent, unbranched ( e.g., bovids)
á
Antlers – bony outgrowth initially
covered in vascularized epidermis, branched (e.g., cervids)
á
Rhinos – horn entirely of keratin
(compacted hair)
Communication
mechanisms:
á
Visual – predator avoidance (aposematism in skunks) or recognition (stotting,
tail flash in Artiodactyla), aggression or submission
(hair erection, facial expression or body posturing)
á
Chemical – sex attractants
(pheromones), individual recognition (usu. sibs or offspring), alarm substances
(released under stressed conditions), territorial (E-efficient alternative to
physical contact)
á
Tactile – grooming reinforces
relationship (e.g., primates, canids)
á
Auditory – territoriality,
aggression, indiv./spp. recognition/location,
distress
á
Echolocation – spp.- or indiv.-unique use of ultrasonic sounds emitted from larynx
(Cetacea) or nose (Chiroptera).
Locomotory adaptations
á
Unspecialized – plantigrade,
all limbs rel. short & segments of equal length (e.g., ursids, procyonids).
á
Cursorial
– digitigrade w/ mass centered over middle
digit, rel. shorter proximal limb segments w/ more muscle mass (e.g., Artiodactyla)
á
Fossorial
– plantigrade w/ heavy claws, fusiform body w/ developed musculature (e.g., talpids)
á
Aquatic – webbed feet or
flippers/fluke, incr. subdermal fat deposits, thick
tail base (e.g., Cetacea,
pinnipeds, otters)
á
Arboreal – long limbs, either
opposable thumbs or hooked claws, stereoscopic vision, some w/ prehensile tail
(e.g., sloths, primates)
á
Aerial – modified hand (homologous
w/ Aves) w/ skin membrane spread across digits (ptagium)
and tail (uroptagium); bats.
á
Volant – dorso-ventrally
flattened tail, skin flaps between appendages for gliding (e.g., Glaucomys)
á
Saltatorial
– rel. lower # of digits and forelimb length, rel. longer tails (used as
a counter-balance; kangaroos, wallabies, kangaroo rat.
Digestive
Specialization – symbiosis & the 4-chambered stomach
á
Most herbivorous mammals are mutualistic
w/ bacteria & protozoans that aid in cellulose
digestion and have complex stomachs to Òre-digestÓ plant material
(ruminants). The rumen temporarily
stores & mechanically digests, the reticulum packages for regurgitation as
Òcud.Ó After chewing the cud, itÕs
passed to omasum for further mechanical digestion,
and then to abomasum for enzymatic digestion.
á
Intestinal length correlated w/ diet ˆ ^ herbivory = ^ length.
á
Separate urogenital
openings except in Prototherians (cloaca
retained).
Note,
that migration (cues & orientation), adaptations for thermoregulation &
mating systems in Mammalia have many similarities w/
those in Aves.
Timing
Parturition
á
Immediate fertilization and implantation
proceed to direct development.
á
Delayed fertilization – peak in
male spermatogenesis out of synch. w/ follicle maturation; usu. in hibernating Rodentia
á
Delayed implantation – copulation
results in fertilization, but zygote doesnÕt implant in uterine lining (so,
development is suspended); can be obligate (e.g.,
Carnivora) or facultative (EST & PRO regulation
of implantation b/c female may be nursing litter from previous mating, e.g., Rodentia,
Insectivora).
á
Delayed development – suspended
development following implantation (e.g.,
so that late-Summer matings donÕt produce offspring
in mid-Winter).
––––
Marvelous morsels mentioning mammals
Morphology
& physiological performance
á
Size range from 2 g (pygmy shrew) to 140
t (blue whale), > 150x BMR
á
Water availability from desert to
oceanic; e.g., kangaroo rat extracts
most water, produces high [urine] using long loops of Henle
in nephron.
á
Temp. tolerance from polar (polar bear)
to desert, e.g., circulatory shunts
and counter-current circulation to minimize core temp. differential w/
environment.
á
Speed adaptations include dorso-ventrally flexible spinal column, non-retractible claws, fixed wrist joints; e.g., cheetah @ 90 km hr-1
Swimming
& diving adaptations (all derived characters, esp. in Cetacea)
á
nostrils on dorsal aspect of head
á
fins/fluke dissociated w/ axial skeleton
(pelvis absent)
á
ability to collapse lung (prevents
nitrogen gas build-up)
á
greater tolerance for ^ [CO2]
and ^ [lactic acid] in blood
á
greater # of erythrocytes and [myoglobin] in blood
á
autonomic decrease in bpm,
circulatory shunt to swimming muscles
Social
systems in mammals
á
Solitary – except during courtship
& mating, e.g., ursids
á
Herds – concentration around
limited resource or increased predator vigilance, usu. w/ temporary hierarchy; e.g., ungulates
á
Packs/prides – cooperative foraging
for large(r) prey, usu. w/ long-term hierarchy; e.g., felids, canids
á
Troops/pods – high levels of social
interactions, cooperative foraging, hierarchy sometimes present; e.g., Cetacea,
Primates
á
Eusociality
– reproductively-dominant female w/ surrogate/mid-wife helpers &
worker caste to locate and retrieve food; e.g.,
naked mole rat
––––
The unity of oppression
– the impact of Homo s. sapiens
Characters
unique to Homo
á
bipedalism – upright posture during
locomotion
á
increase in rel. brain mass –
metabolically expensive, so foraging efficiency had to increase.
á
Language – reqÕd change in
breathing control, position/size of larynx
Humans
monitoring vertebrate populations
Scan
surveys
Mark-recapture
surveys – mark in a way that doesnÕt affect spp. mobility
Collections
Radio-telemetry
– sometimes invasive, but not lethal
Tissue
sampling – invasive but not lethal, assoc. w/ DNA analyses
Humans manipulating vertebrate
populations
1.
Encroachment – habitat manipulation affects area-sensitive species
2.
Hunting –
Predator
control: Canis, Ursus
Pest
control: Odocoileus, Rodentia, Canis, Procyon, Didelphis
Subsistence
– kills for food, Bison
Sport
– kills for recreation, Odocoileus,
Melagris, sciurids, fish, Crotalus
Commercial
– kills for profit, mustelids, lagomorphs
3.
Commercial harvest – profit-based removal from habitat w/out killing (pet
trade, research labs, circuses)
4.
Non-native introductions
a) Tilapia zillii (striped tilapia) –
imported by gov't/private agencies since '50's for fish ponds and/or
controlling aquaphytes, and invert. pests. Effects include displacement of native fish spp. and
predation on native aquaphytes.
Eradicated from Fla. & Nev., but established populations remain in ³
6 states.
b) Boiga irregularis (brown tree snake)
– accidental introduction to Guam via post-WWII troop movements. Presently > 1,000,000 indiv's.
(31,000 km-2). Effects
include power outages & extinction/extirpation of > 20 native vert. spp.