5580

locomotion and lung ventilation

Air moves between the lungs (arrow), but little or no air moves into or out of the animal. Sustained locomotion requires separation of respiration from locomotion.

problems with morphological characters

(1) Incomplete fossil record • There are gaps in the records of many taxa • Sometimes millions of years long

Problems with molecular characters

(1) Not all are equally useful • Some indicate short-term changes; other indicate long-term changes • Mixing the two can produce misleading results (2) Not applicable to fossils • Fossils seldom yield molecules • Addition of a new fossil can rearrange a morphology-based phylogeny • Molecular phylogenies can't be tested this way (3) Dating diverge times is difficult • Based assumptions about rates of molecular mutation Problems with Molecular Characters 15

Basic scaling rules

(1)Surface area increases as the square of the change in linear dimensions . (2)Volume increases as the cube of the change in linear dimensions.

palatal teeth

-> reduced/lost in more derived amniotes -> absent in most extant amniotes

defintion of synapsid

1 temporal bar

Maintaining body temps different from air temps requires Thermoregulatory mechanisms:

1) Ectothermy: gaining heat from external sources, e.g. basking in the sun or resting on a warm rock. 2) Endothermy: gaining heat from internal sources, i.e. metabolic production of heat

alternative phylogenies for eutheria

1) afrotheria is basal to all other eutherians 2) xenarthra is basal to all other eutherians Placentalia=infraclass Afrotheria, Xenarthra, Boreoeutheria= superorder

3 major continental movements

1) cambrian fragmentation 2) devonian coalescence 3) late cretaceous fragmentation

Grassland plants present herbivores with two problems

1) difficult to digest due to high cellulose and lignin content 2) cause rapid tooth wear due to high silica content

Boreoeutheria

1) euarchontoglires 2) laurasiatheria

Chorioallantoic placentas

1) hemochorial placenta 2) endotheliochorial placenta 3) epitheliochorial placenta

Evidence that cetaceans were artiodactyls

1) molecular evidence 2)fossil evidence -astragalus ankle in two different prehistoric whales

The problem of foregut fermentation: balancing constraints

1) rumen capacity 2) energy requirements 3) nutrient requirements

hominin derived skeletal traits

1) skull attaches inferiorly to vertebral column 2) bowl-shaped pelvis 3) barrel shaped rib cage and distinct waist 4) larger valgus angle 5) s-shaped vertebral column 6) non divergent hallux

fully aquatic animals have only evolved three times

1)Sirenia: manatees Never come to land Herbivorous 2)cetacea whales, dolphins, porpoises never come to land carnivorous 3)carnivora: pinnipeds: seals, lions, walrus amphibious: come to land to breed, give birth carnivorous

If an animal increases in size isometrically:

1. Weight would increase as the cube of its linear dimensions 2. Cross section of its bones would increase only as the square of its linear dimensions --This wouldn't work since limbs are unable to support the increased weight

Two mechanisms for increasing sound pressure: "impedance matching

1. area effect 2.lever effect

2 major evolutionary lineages of amniotes

1. sauropsids (reptiles, including birds) 2. sunapsids (mammals) -Parallel but independent origins of basic characters, e.g. lung ventilation, kidney function, insulation, temperature regulation

milk compisition for whales and seals

12x higher in fats and 4x richer in proteins than that from domestic cows

pharyngeal formula for Therapsids

2:3:3:3:3

pharygneal formula for pelycosaurs

2:3:4:5:3

Temporal fenestration

3 different lineages of amniotes are identified based on the number of holes in the head

how old is earth?

4.6 billion years old

modern synthesis

A comprehensive theory of evolution that incorporates genetics and includes most of Darwin's ideas, focusing on populations as the fundamental units of evolution.

Polyphyletic taxon

A group composed of a collection of organisms in which the most recent common ancestor of all the included organisms is not included, usually because the common ancestor lacks the characteristics of the group. Polyphyletic taxa are considered "unnatural", and usually are reclassified once they are discovered to be polyphyletic.

paraphyletic taxon

A group composed of a collection of organisms, including the most recent common ancestor of all those organisms. Unlike a monophyletic group, a paraphyletic taxon does not include all the descendants of the most recent common ancestor.

Isometry

A transformation in which the preimage and image are congruent

Advantages of terrestrial activity

Access food Escape aquatic predators Both would increase the survival of adults and their offspring

______________possess remnants of genes known to be required for testicular descent

Afrotherians; These are nonfunctional relict genes(pseudogenes)

Middle ear

Air-filled space between the eardrum and the inner ear

Infrared radiation

All objects (animate & inanimate), radiate energy at wavelengths determined by their absolute temp • Objects in the temp range of animals and the Earth's surface radiate in the infrared portion of the spectrum • Animals continuously radiate infrared heat to the environment and receive infrared radiation from the environment. • Infrared radiation can lead to either gain or loss of heat, depending on relative temp of animal & environmental surfaces

Anthropod origins

All tiny eosimiids stem anthropoids, 12 g predated the split between catarrhines and platyrrhines

Heterometry

Alteration in the level of gene expression during development

A derived character is called?

An apomorphy; away from the ancestral condition

monophyletic lineages

An evolutionary lineage with a single evolutionary origin, i.e., an ancestor and all its descendants

facilitation

An interaction in which one at least one species benefits and none lose

Shared ancestral character

Ancestral character shared by ≥ 2 taxa -- Vertebral column is a Symplesiomorphy in vertebrates

Dispersal via rafting

Animals trapped on floating islands of vegetations rafting event

Homologous character

Any character (trait) that species share by inheritance from a common ancestor that also possessed it. A character with a single evolutionary origin

homologous character

Any character(trait) that species share by inheritance from a common ancestor that also possessed it. A character with a single evolutionary origin

One hypothesis for extinction

Asteroid impact led to a massive release of methane generating rapid global warming inhospitable to life.

Why is frugivory linked to the evolution of binocular vision?

Because stereoscopic vision is necessary for seeing cryptic objects against a background

Gigantothermy

Bigger animals have more stable body temperatures

Which of the following mammals is most closely to Cetaceans?

Bisons

Cetaceans and Artiodactylas are now often grouped together in the single order:

Cetartiodactyla

Ancestral character

Character that DOES NOT differ from ancestral condition --Plesiomorphy

Which character is ancestral vs derived?

Compare the characters of the ingroup(organisms under study) to those of an outgroup

Key mechanism driving speciation, diversification, and radiation

Continental drift

The temporalis muscle connects the

Coronoid process to the temporal fossa

Fossil evidence indicates that the three major lineages of extant mammals originated during which Period?

Cretaceous

extant lineages of crown group mammalia originated during what period?

Cretaceous

How did the mammal ear originate?

Current hypothesis: Early synapsids detected sounds via bone conduction: Sound waves received by the lower jaw and transmitted via the angular, articular, and quadrate bones to the stapes and inner ear • Pelycosaur stapes appears to be more of a structural brace than a sound conductor. • Low-frequency sound received via intra-bone conduction, from mandible to quadrate and quadrate to stapes

The evolution of the definitive mammalian middle ear involved

Decreasing size of the middle ear bones, and increasing size of the tympanic membrane

shared derived character

Derived character shared by ≥ 2 taxa and inherited by a common ancestor -Synapomorphy

parallel evolution

Development of similar characters among species that recently diverged

sauropsids

Diapsids and Anapsids

Ameridelphia

Didelphimorphia: Opossums: found mainly in the Neotropics, 1 North American species; Diversity was highest mid-cenozoic Paucituberculata

What was key to early radiation of tetrapods in the late carboniferous period?

Diversification of insects

binomial nomenclature

Each species is assigned two names: one identifying the species itself and the other the genus to which the species belongs.

Plate tectonics

Earth's crust (continents & seafloors) is made of rocky plates that float on denser, partially melted rock. • 10 majors plates and many minor ones, separated by ridges, trenches, or faults.

Xenarthra and afrotheria may be more closely related to boreotheria which means?

Either one may be 1) the sister taxon of Boreotheria 2) Basal to all other placentals

Laurasiatheria

Elipotyphla -originally known as Insectivora, include tenrecs, golden moles, elephant shrews, tree shrews molecular data placed these species in other orders Fereungulata-largest grouping Artiodactyla Perissodactyla Cetaceans Carnivora pholidota

Late Cretaceous Fragmentation

Epicontinental Seas - Act as Barriers

What's the difference beteen an era, period, an epoch?

Era: Paleozoic, Mesezoic, Cenozoic Period Epoch: 252 (Permian-Triassic) 66(Mesozoic- Cenozoic) and (cretaceous- Paleogene)

Evaporation

Evaporation of water occurs from the body surface and from the pulmonary system • Each gram of water represents about 2450 joules of heat • Evaporation of water transfers heat from the animal to the environment and thus always represents a loss of heat.

heterochrony

Evolutionary change in the timing or rate of an organism's development.

Systematics

Evolutionary classification of organisms

African lungfish

Exhibits tetrapod-liked gaits, including walking and bounding (uses a primitive lung to breathe

Triassic Jurassic importance

Extinction event, set stage for dinosaurs

End-Triassic importance

Extinction vacated terrestrial niches, set stage for dinosaurs

estrous cycle steps

FSH initiates follicular development within the ovary estrogens- secreted by the follicle- cause thickening of the endometrium LH cause the egg to burst from the follicle(ovulation) GnRH Estrogen/progesterone stimulates uterus to thicken and progesterone stimulates growth of mammary glands

Fereungulata is the smallest grouping within Laurasiatheria

False

Most of the defining characteristics of mammals originated in the Cenozoic Era

False Triassic Era

________in an order stem from a ______________ and retain still fewer characteristics in common.

Families; still more remote ancestor;

How are fins made into limbs?

Fins and limbs are made into homologous structures, coded for by the same set of Hox genes.

Solar radiation

For most animals, the sun is the primary source of heat, and solar energy always results in heat gain. • Solar radiation reaches an animal directly when its standing in a sunny spot, and indirectly via reflection from clouds, atmospheric dust, and objects in the environment

consequences of maintaining high blood pressure

Forces some blood plasma (liquid part of blood) out of capillary vessels and into intercellular spaces of body tissues • Fluid is recovered and returned to circulatory system by the lymphatic system • ALL tetrapods have a lymphatic system

_________in the same family share fewer characteristics because each has departed further from their __________________

Genera; remote common ancestor;

Plesiadapiforms

Generalized aboreal primate small brain no post orbital bar retained claws

Xenarthra Prehistoric diversity

Glyptodonts -Ground Sloths

Enlarged temporal fenestra and loss of the orbital bar are interpreted as feeding adaptations that fuel a relatively higher metabolic rate because they allow:

Greater volume of jaw adductor muscles

Autopod

Hands/feet with digits Function: holdfasts and pivot points; provided frictional contact with the ground

Conduction

Heat transfer between the animal and a solid material(e.g. substrate) Results in heat gain or heat loss: 1) heat loss= substrate temp< animal surface temp 2) heat gain= substrate temp> animal surface temp Can be modified by changing: 1) the surface area of the animal in contact with the substrate 2) the rate of blood flow in the parts of the body in contact with the substrate

Climate Patterns Across the Phanerozoic

High 02, low CO2 and temp

Scales, hairs, etc. are what?

Homologous. • All develop from a common epidermis: anatomical placode (shared ancestral character of amniotes) • All express a similar suite of developmental signaling molecules • Hair & Feathers are not independently derived structures and they DID NOT evolve from Scales. • A change in gene expression in development caused the anatomical placode to produce different type of epidermal structures from the same primordium (ancestral tissue structure)

What led to insect diversification?

Increase in terrestrial vegetation

What is the function of the corpus luteum

Inhibits gonadotropin releasing hormone GnRH ) and maturation of new follicles

What is the northernmost living extant nonhuman primate?

Japanese Macaque

extinct lineages of crown group mammalia originated in what period?

Jurassic

Mesozoic Mammal Radiations

Jurassic Early Cretaceous

Hierarchy in the Linnaean System

Kingdom, Phylum, Subphylum Class, Order, Family, Genus, Species -did king phillip cry out for goodness sakes?

Consequence of monotremes diverging early?

Laurasia: Boresphenidans Gondawana: Australosphenidans -- Stem monotremes, other extinct groups Consequence: retain basa characteristics

Devonian coalescence

Led to the supercontinent: Pangea was mid-Carboniferous to mid- Jurassic

morphological adaptations for aquatic living

Locomotion 1)paraxial swimming typical of semiaquatic mammals relatively inefficient use limbs 2) axial swimming typical of fully aquatic mammals undulations of body and tail. relatively efficient

Late-Triassic importance

Mammaliaforms appear, first appearance of the dinosaurs(small, carnivorous therapods)

Metatheria

Marsupials; Give birth to live young; short gestation time produces very immature young that continue development attached to nipple often in pouch. Marsupials dominate the mammalian fauna only in Australia

Both ____________and ________________have a placenta

Metatherians and Eutherians;

when did Glaciers regress?

Mid-Permian; Ice-free world persisted until the mid- Cenozoic -Largest "ice-house to hot-house" transition

Phylogenetics recognizes only?

Monophyletic lineages

Prototheria

Monotremes -Retain the generalized amniote reproductive feature of laying eggs. -Extant monotremes are 4 species of echidna and the platypus

Great American Interchange

More animals moved south than north Today, opossums, porcupines, and armadillos are the only southern immigrants established north of the Rio Grande 50% of extant South American genera are from North American immigrants

Is the pectoral girdle connected to the head?

NO

Are wings a homologous character among bats and birds?

No, wings evolved independently in these separate lineages, which diverged long ago. • This is an example of convergent evolution

Permian-Triassic Importance

Non-Mammalian Synapsids Dominate

Where did "true" primates originate?

North America and Eurasia

stem primates

Northern Hemisphere Plesiadapiforms Early paleocene-eocene

Structure of Amniote Bone

Not uniform: dense outer layer, spongy inner layer Articular cartilage reduces friction as the joint moves--> arthritis

amniotes climate patterns across the phanerozoic

O2 above, Temps below present, Co2 at present

No convincing explanation of the ________of the Amniotic Egg

Origin Extraembryonic membranes not preserved in the fossil record

Euprimates originated near the boundary between which two Epochs?

Paleocene-Eocene

In what era did the tetrapods, amniotes, and synapsids originate?

Paleozoic

Which kind of group is artiodactyla?

Paraphyletic. It includes the common ancestor but not all of the descendents. Excludes the cetaceans which are believed to have evolved from an artiodactyl ancestor and are most closely related to hippos among living forms

Eutherians

Placentals; Placenta: structure that transfers nutrients from the mother to the embryo and removes waste products of the embryo's metabolism

axial muscles function in tetrapods

Postural support Lung ventilation

Terrestrial Tetrapods climate patterns across the Phanerozoic

Present O2, still slightly above present CO2

costal ventilation

Produces a pressure differential large enough to draw air down a long thin tube such as the trachea in the necks of amniotes.

Synapsids mammal types

Prototheria- Monotremes Metatheria- Marsupials Eutheria- Placentals

Function of temporal fenestration?

Provide room for muscles to bulge Modify complexity and orientation of the jaw-closing (adductor) muscles

The crurotarsal joint emphasizes fore-and-aft movement of the leg because it involves a plane of motion between which bones?

Proximal tarsals (astragalus/calcaneum) and fibia/tibia

Which of the following skeletal characteristics is NOT an adaptation for improved locomotion?

Reduced clavicle and interclavical 3 or more sacral vertebrae Large pubis and ischium Shorter tail

Underlying reason for skull fenestration

Reorientation of the adductor mandibularis to enhance feeding

reversal

Return to an ancestral form; can produce similar structures in distantly related organism

Heat radiating outward from the Earth's core creates convection in mantle rock?

Sea floor spreading: pushes land masses to or away from one another When plates collide, they form mountains or subduction zones

Amniotic egg features

Shell permits movement of water vapor, O2, and CO2 Must be deposited in air • Albumen (egg white): protects against mechanical damage; provides water & protein • Yolk sac: energy supply • 3 extraembryonic membranes derived from the embyro

Anthropoidea is synonymous to what?

Simiiformes

which blood circuit do fish have?

Single circuit; Two chambered heart: one atrium and one ventricle Atrium collects blood returning from body • Ventricle pumps blood to gills where gas exchange occurs and blood is re-oxygenated (gill circulation). • Blood then continues through the rest of the body before arriving back at the atrium = SYSTEMIC CIRCULATION. • Unidirectional flow of blood produces a gradient of oxygenated to deoxygenated blood around the fish's systemic circuit. • This limits the amount of oxygen that can reach organs and tissues, reducing overall metabolic capacity

Tetrapod Skeleton

Skeleton that can support body Legs and feet that can transmit backward force to substrate Rigid bones

Derived characters of amniotes

Skin elaborations Amniotic egg scales, hair, feathers, etc. are homologous costal ventilation of the lungs temporal fenestration

Diversification is an outcome of what?

Speciation

Hypothesis of common descent

Species diverge gradually and to an indefinitely great extent from common ancestors -Nested series of ancestor-descendant relationships trace the evolutionary history of a group of organisms

The most abundant terrestrial vertebrate in the late carboniferous and entire Permian periods?

Synapsids

Permian importance

Synapsids are the dominant terrestrial tetrapod

amniotes

Tetrapod that produces an amniotic egg mammals, birds, reptiles

How does a land animal evolve in water?

Tetrapod traits were advantageous for animals that were still living in water. • Lobed fins may have been useful in slow stalking behavior in shallow water; digits, wrists, and ankles may have promoted maneuverability

Most synapsid lineages disappeared by the end of the Permian because?

The Permian extinction. 80% of all species were eliminated. The biggest extinction event in Earth's history, 252 MYA.

amniotes have what in embryo?

Three extraembryonic membranes -derived from the zygote, but separate from the embryo itself 1)chorion (outer membrane) Gas exchange 2) allantois (inner membrane) - waste storage, gas exchange 3) amnion (innermost membrane) -cushions and protects embryo

Most derived tetrapodmorph Fish:

Tiktaalik Fills a morphological gap between fishes and tetrapods; its fins indicate it was on the fish side of the fish-tetrapod transition

Scandentia

Tree shrews "Potental" next closest relatives of primates (including humans)

Mammaliaformes originated during which Period?

Triassic

A diverse pattern of extinction and survival of tetrapod lineages at the K-Pg boundary suggests that asteroid impact was not the sole cause of the K-Pg extinction. true or false?

True

Tetrapods

Vertebrate descended from a four-legged ancestor; this includesanimals that have returned to life in the water mammals, birds, reptiles, amphibians

Further separation of the continents produced?

Vicariant isolation

Can the same character be synapomorphic or symplesiomorphic?

Yes, depending on the taxonomic comparison: A vertebral column is a symplesiomorphy among vertebrates -Provide NO info. about evolutionary relationships of vertebrates to one another. A vertebral column is a synapomorphy when vertebrates are compared to invertebrates -Provides info. about evolutionary relationships between vertebrates & invertebrates

are elephants related to manatees and dugongs?

Yes, some early proboscideans have anatomical features that suggest a semiaquatic existence later proboscideans may represent a secondary return to a more terrestrial existence from an originally aquatic stock.

Axial skeleton: vertebrae and ribs

Zygapophyses interlock, resist torsion and compression Cervical vertebrae allow head to move up/down, right/left

The masseter muscle connects the:

Zygomatic arch to the masseteric fossa

clade

a monophyletic taxon

outgroup

a reference group that is less closely related to the ingroup than the members of the ingroup are related to eachother

Light bars indicate

absence of fossils but taxon assumed present because fossils are known from earlier times.

What is the geographic distribution of extant Catarrhines

africa and asia

3 major groups of eutherians

afrotheria(africa) xenarthra boreoeutheria

when did extant orders of mammals diversify?

after K-PG boundary Driver of KT mass extinction

dichromatic (two pigments) vision

all eutherians lack RH2 and SWS2 which limits ability to distinguish colors

sacral vertebra connected to pelvic girdle function

allows hindlimbs to transfer force to the axial skeleton 1 sacral attachment in basal tetrapods mammals usually have 2-5 sacral vertebrae humans have 5 sacral vertebrae fused together to form the sacrum

what are toxic waste products of proteins?

ammonia highly toxic

amniote distinguishing character

amnion: inner layer surrounding the embryo; derived from the embryo itself

shared derived characters of amniotes

amniotic egg skin elaborations from keratin costal ventilation of the lungs palatal teeth mesotarsal joint(aka intratarsal joint)

impedance matching

amount of sound energy conducted by medium

Middle ear function

amplfiy and transmit sound waves to the inner ear

Cross-sectional area of a limb supports?

an animal's weight on land

ureter

ancestral character of amniotes

anapsids have what?

ancestral reptiles; no temporal fenestra

_________________________________contributed to the early diversification and radiation of mammals.

angiosperm radiation and dinosaur extinction

Extant vertebrates

animals with backbone and skull

Mammalia

any species descended from the last common ancestor of Prototheria, Metatheria, and Eutheria

Endothermy and ectothermy ________ mutually exclusive

are NOT; many aniimals do both.

occipital condyle function

articulates with the atlas to form a hinge joint that allows flexion and extension of the head

Two major groupings of eutherians

atlantogeneta -afrotheria -xenarthra Boreoeutheria

Mesotarsal joint

axial locomotion ankle joint lacked a distinct plain of motion appendicular(limb-based) locomotion distinct ankle hinge joint allows for propulsive lever motion

Skull differences between Metatherians and eutherians

basal dental formula for eutherians 3/3, 1/1, 4/4, 3/3 (x 2) = 44 teeth many eutherians have fewer teeth, e.g. humans

monotremes characteristics

basal shoulder girdle -- retain interclavicle and large coracoid -- lack scapular spine and supraspinous/infraspinous fossae

Chiroptera

bats were originally placed with euarchontans Molecular data place them in Laurasiatheria

Why is acoustic impedance of water greater than air?

because water is denser than air. More pressure is required to transmit sound through water More pressure= less impedance

Bone diameter scales with positive allometry:

bigger animals have proportionally thicker limb bones than smaller ones

defining hominin trait

bipedalism

Evolution of Bipedalism traditional hpothesis

bipedalism was an evolutionary response to the spread of african savanna environments. bipedalism originated in the savannas, and was an adaptation to savanna living knuckle walking was a precusor to bipedalism

which tetrapods have the highest blood pressure?

birds and mammals. Why?

parturition

birth

placenta functions

built from extraembyronic membranes 1) physically anchors fetus to uterus 2) transports nutrients from the circulation of the mother to the developing fetus 3) excretes metabolites of the fetus into the maternal compartment 4) produces hormones that regulate organs of the mother and fetus -suppresses the normal immune response that hte mother's body would normally mount aginst the placenta and fetus, which are genetically alien to the mother --chorion produces lymphocytes and protein that block mother's immune response --the placenta is therefore an allograft: a successful foreign transplant

Bone conduction

by direct route through the dentary to the postdentary bones or by indirect route through the rest of skull - is a major transmission route of sound waves to the inner ear in synapsids.

Carnivora

caniformia feliformia

what are carbohydrates made up of?

carbon, hydrogen, oxygen HOC

In which period did the tetrapods, amniotes, an synapsids originate?

carboniferous

Carnivora physical trait distinguishes carnivorans from other carnivorous mammals?

carnassial pair

carnivore vs herbivore skull musculature

carnivore: jaw joint on same level as tooth row

What is the geographic distribution of extant Platyrrhines

central and south america

apomorphy

character that differs from ancestral condition

plesiomorphy

character that does not differ from ancestral condition

Plesiomorphy

character that species have inherited unchanged from their ancestors --Carnassial teeth

Vomeronasal organ

chemosensory organ in the roof of the mouth of most tetrapods(except birds) in some mammals, males use it to inhale pheremones to asses female reproductive status(flehmen behavior) remnant may exist in humans

Which two extraembryonic membranes form the placenta of Eutherians?

chorion allantois

xenarthra orders

cingulata(armadillos) pilosa(sloths and anteaters) edentates because they do not have incisors and lack or have poorly developed molars

Dermopterans

closests relatives of primates flying lemurs--don't fly and aren't lemurs

key component of milk

colustrum first product released by the mammary gland following birth protein-rich fluid containing antibodies that confer mother's resistance to various diseases to the young

The definition of Mammalia is any species descended from the last _______________ of ____________ mammals.

common ancestor; extant

Homoplastic similarities do not indicate ____________

common ancestry • They can obviously complicate the process of determining evolutionary relationships.

which ventricular septum do mammalian synapsids have?

complete

Mammals and birds have which ventricular septum

complete and each lost a systemic arch

which kind of ventricular septum do derived amniotes have?

complete or partial venctricular septum

Early eocene

connectivity between Asia, North America, and Europe via the Bering bridge and Greenland respectively Separation between Eurasia, Africa, South America Separation between North and South America

what kind of evolution was the ciruclatory sytem in mammals and birds

convergent evolution

fermentation

conversion of sugars into inorganic acids and alcohols in the absence of oxygen

Which of the following is NOT a characteristic of mammals that originated in Cynodonts?

crurotarsal joint zygomatic arch bowed out Diphyodont dentition masseteric fossa on dentary

hypotheses for why testicles descend

dangling gonads are a way to signal virility and good health.

Describe the trend in average body size of synapsids from the end Permian to the end Triassic.

decreasing

Synapsids characteristics

decreasing body size improved locomotion improved food processing improved hearing

DMME

definitive mammalian middle ear; Three auditory ossicles completely detached from the mandible. The DMME is the defining characteristic of mammalia

Groups can only be identified on the basis of ________________

derived characters; -- Characters that have the same evolutionary origin (are homologous) that differ from the ancestral condition (are derived).

Which group is most closely related to primates?

dermoptera flying lemurs

problems with a high cellulose diet

diets are rich in carbon, but low in protein most of the carbohydrates are locked in indigesetible cellulose, and the proteins exist in chemical compounds herbivores depend on specialized bacteria and protozoans living in the digestive tract to digest cellulose and protein these organisms also synthesize fatty acids, amino acids, proteins, and vitamins. that can be absorbed and used by the animal host

Different lung structures may refect ?

different O2 concentrations

Different physical properties of air and water result in ___________________________ acting on terrestrial and aquatic vertebrates

different selective forces; A key difference is the effect of gravity on support and locomotion

Hands and feet are a property of ______________________ already present in fishes; no new genetic information required

differential expression of genes

adaptive radiation

divergence into different adaptive forms; taxa usually differ in use of resources or habitats -Hawaiian honeycreepers

sea lions locomotion

dorsoventral movements of the back and hindlegs derived type of axial swimming

which blood circuit do tetrapods have?

double circuit; • SYSTEMATIC CIRCUIT supplies OXYGENATED blood to the BODY • PULMONARY CIRCUIT supplies DEOXYGENATED blood to the LUNGs • More separation of oxygenated/deoxygenated blood; metabolic efficiency

Which groups have the double and single pulley astragalus

double= artiodactylas single= perissodactylas

eutherian uterus

duplex, bipartite, bicornuate simplex

Catarrhine trichromatic vision comes from?

duplicaiton of the LWS opsin gene into an L form with maximum sensitivity at 530 nm (more sensitive to green) and M form with maximum sensitivity at 563 nm (more sensitive to red)

for many mammals the composition of milk changes during the course of lactation

early and late stages of lactation -more protein/ less sugar middle stages less protein/more sugar

Euprimates

early eocene of North america and eurasia defintiive evidence that euprimates reached africa by the mid-eocene

Convergent evolution

ecologically similar species originating in different areas from different ancestors

Monotreme characteristics

edentate electroreceptor bill cloaca platypus genome has more bird characteristics than therian genome

ovulation

egg(s) released from the ovaries

gestation

embryo develops within placenta

afrotheria

endemic group of african mammals indicative of a long period of independent isolated evolution of mammals on the african continent consistent with cenozoic geography: Africa was isolated from Eurasia during first half of the era( until Miocene)

modern primates limbs and digits

enhanced digit mobility leaping claws compress into nails sensile tactile pads on distal ends of digits

Rigid bones

enhanced remodeling capacity(adaptation to increased stress) Internal structure continuously changes: activity increases bone mass Allows broken bones to heal

In Amniotic tetrapods, ___________& ____________muscles are ________________; allows lung ventilation

epaxial; hypaxial; differentiated

In fish & modern amphibians, _______muscles (dorsal side of trunk) & ________muscles (ventral side of trunk) are _________________

epaxial; hypaxial; undifferentiated

which group has a post-orbital bar?

eutherians metatherians don't

stem eutherians are

eutherians outside the grouping of the extant orders

speciation

evolution of reproductive isolation within an ancestral species, resulting in two or more descendant species

heterotropy

evolutionary change of physical location of a developmental process

Diversification

evolutionary increase of the number of species in a lineage. Usually accompanied by divergence in phenotypic characters

Eutherians chorioallantoic placenta

extensive villi, strong connection to uterine lining, increased surface area for rapid and efficient exchange of nutrients, gases, and wastes feedback from the eutherian placenta maintains the life of the corpus luteum, suppresses ovulation, allows extension of gestation past a single estrus cycle

Current research indicates that internal testes in Afrotherians and Xenarthas is an ancestral trait.

false

Feedback from the metatherian placenta maintains the life of the corpus luteum , suppresses ovulation, allows extension of gestation past a single estrus cycle

false

In non-amniotes & basal amniotes, the urinary, alimentary, and reproductive tracts exit the body via two openings

false

The middle ear of extant members of Mammalia is connected to the dentary bone true or false

false

True seals can turn hindlegs forward & move on land with vertical flexions of the vertebral column.

false

the nipple or teat is a characte found in all extant mammals true or fals?

false

milk composition

fats proteins lactose(milk sugar) vitamins salts

Foregut fermentation product

fatty acids

marsupium

female abdominal pouch poor diagnostic feature not all marsupials have a marsupium echidnas have a marsupium

Mate selection

female choice of traits linked with quality -physical appearance -sounds -smells

delayed ovulation -sperm storage

female stores sperm until after hibernation is over and then ovulates the rest of the reproductive cycle is as normal

copulation

female/male mating

epitheliochorial placenta

fetal tissues contact the lining of the uterus but do not penetrate it ungulates and non-anthropodi primates

endotheliochorial placenta

fetal tissues penetrate lining of teh uterus, but not the lining of the maternal blood vessels carnivorans and elephants

amniotic egg probable ancestral condition

flexible leathery eggshell

Two systems for breaking down cellulose

foregut fermentation(mouth to intestine) hindgut fermentation (intestines)

Allopatric speciation

formation of a new species from ancestral species due to the geographic separation of the breeding population

encephalization quotient

frugivorous diet may be linked to to increase in this -brain size in relation to body size

chorioallantoic membrane

fusion of the chorion and allantois membranes

vicariance

geographic isolation of populations of a once-widespread species by development of a physical barrier within the ancestral species range -Geographic isolation leads to speciation -Gondwana Marsupials

euarchontoglires

glires -rodentia -lagomorpha Euarchonta -scandentia -dermoptera -primates

continental drift impacts

global climate variation faunal interchange

xenarthra prehistoric diversity

glyptodonts ground sloths notoungulates: all extinct

_______and _______are low in _________and high in _______

grass stems and sheaths low in protein high in lignin

convection

heat transfer between the animal and the air(or water) Results in heat gain or loss: 1) Heat loss= air temp< animal surface temp. 2) heat gain=air temp> animal surface temp When the air is moving the rate of heat exchange is greatly increased

Foregut fermenters( ruminants) are adapted to using

high quality foods;

milk composition for northern mammals

high-fat, high protein milk young of these animals need to increase weight quickly to avoid cold after they are weaned

fetal cetaceans have ____________that form then disappear

hindlimb buds

morphology of cetaceans

hindlimb lost, vestige of the pelvis remains -muscles run from vestigial pelvis to genitals compressed neck vertebrae zygapophyseal articulations lost between vertebrae in trunk and tail no sacral vertebrae long fingers

Convergence, parallelism, and reversal are forms of

homoplasy;

Hominine

humans, chimps, gorillas, and extinct forms more closely related to these taxa than to orangutans Homo sapiens is the only extant species

morpohological data indicated interrelationships between?

hyraxes, sirenians, and proboscideans

pelvic girdle

ilia connects limbs to vertebral column

How does the middle ear function?

impedance matching

Where does the pectoral girdle rest?

in a muscular sling. Does not articulate directly with vertebral column

alternatives: induced ovulators

in some species, like cats and some rodents, copulation comes first. copulation triggers ovulation in these species

crown group

include extant species AND fossils that have all of the derived characters of extant species (monophyletic)

stem groups

include fossils with some derived characters (paraphyletic)

Dual use of axial muscles for locomotion and ventilation can be?

incompatible; When a lizard runs it has difficulty using its ribs for lung ventilation

area effect

increase ratio of the area of the tympanic membrane to that of the oval window. As the ratio increases, sound pressure increases

when linear dimensions double, volume

increases eightfold. --an animal 2x as tall as another is 8x as heavy

Which of the following skull features first seen in cynodonts functions as a pathway for sensory nerves from the snout to the brain?

infraorbital foramen

corpeus luteum produces progesterone and estrogen that _______________and maturation of new follicles

inhibit GnRH ;

Trapezius muscle derives from fish gill musculature

innervated directly from the brain via cranial nerves; not by spinal cord people with spinal injuries can still shrug shoulders other remnants of the brachiometric musculature in the larynx and vocal chords allow quadriplegic people to control prosthetic devices

lympathic system mammals- lymph nodes

intercept pathogenic material, e.g., cancer cells

Narrow blue lines show?

interrelationships only; they do not indicate: times of divergence nor unrecorded presence of taxa in the fossil record

Coprophagy

lagomorphs ingest fecal material for further extraction of nutrients

why do larger mammals have more stable body temperatures than small mammals?

larger animals have a smaller surface area to volume ratio which results in less heat loss and a more stable body temp

Hominin derived cranial traits

larger brain case vertical forehead reduced brow ridges and sagittal crest larger nose shroter rostrum

When did extant orders of mammals originate?

late cretaceous. before KPG Angiosperms--> cretaceous terrestrial revolution(KRT)

_______are high in __________and low in __________

leaves and forbes; high in protein low in lignin

Bigger animals exchange energy with the enviroment________rapdily than smaller species

less; Bigger animals exchange energy with the environment less rapidly than smaller species

Which of the following hormones causes the egg to burst from the follicle, i.e., ovulation

leutanizing hormone

Olecranon process on ulna function

lever for the extensor muscles that straighten the elbow joint

Locomotion=

limb movements, NOT trunk bending

Appendicular skeleton

limbs and limb girdles(pelvic, pectoral) in bony fish, pectoral girdle is joined to head

Tetrapod distinguishing character

limbs with carpals, tarsals, and digits

monotreme sexes urogenital system

little differences between the sexes, other than the uteri and ovaries in place of internal testicles retained within the abdomen

axial muscles in lizards and salamanders

locomotion due to bending the backbone laterally

evolution of bipedalism alternative hypothesis

locomotion of extant great apes and humans derived from a large ancestral ape capable of hand-assisted aboreal bipedalism with extended lower limbs Orangutan ancestors became arboreal specialists, moving mostly aboveground in tropical forests • Ancestors of gorillas and chimpanzees, in response to changing habitats, moved vertically in and out of trees, and thus independently acquired knuckle walking • Hominins retained existing adaptations for extended-limb bipedalism and eventually became committed terrestrial bipeds.

Small ruminants have relatively greater metabolic demands, and the necessary ___________________________in the rumen means they have t consume_________________

long retention of food high quality forage(low fiber/ high degestibility)

tetrapod adaptations

longer snout; tongue; salivary glands simple tidal-flow lung stouter ribs urinary bladder middle ear -- independently derivedi n non-amniotes and amniotes

The heat capacity of air is?

low; as is its ability to conduct heat

Hominoidea vs cercopithecoidea derived dental traits

lower molars have 5 cusps--hominoid cercopithecoid-4 cusps

locomotion in birds and mammals

mainly due to limb movements

Solution for Consequences of Maintaining High Blood Pressure

maintain different blood pressure in the systemic(body) and pulmonary (lung) circuits

tetrapod solutions for gravity pools fluids

maintain high blood pressure with powerful heart have valves in limb veins that resist backflow

Amniotes definition

mammals and reptiles

synapsid

mammals; amniote descended from an ancestor with a single large opening in the skull

Main difference between metatherians and eutherians

marsupials have epipubic bone- pouch, locomotion function?

hemochorial placenta

maternal blood in direct contact with fetal tissues probable ancestral condition

stem placentals were thought to have been limited to which period?

mesozoic New evidence indicates some early Cenozoic eutherians(e.g. Taeniodonta) fall on the placental stem

Small ruminants have higher ____________relative to their rumen size than do large ruminants

metabolisms

Differences between miocene platypus and modern platypus

miocene= small infraorbital canal modern platypus= larger infraorbital canal; better developed electrosensory system

Newer character approach

molecular characters -base sequences of mitochondrial and nuclear DNA -functional significance is usually unknown -massive number of characters -computer-based analyses

anthropoids

monkeys, apes, and humans derived traits: diurnal (except for owl monkeys) brachiation : swinging from the underside of one branch to the underside of the next using hands to grasp branches

Prosimians

more forward-ooking orbits aboreal life, slender hindlimbs

classic character approach

morphological characters; anatomical traits functional significance is known small number of characters human-based analyses

clavicle retained in which group

most Therians but lost in many cursorial eutherians

artiodactyla

most diverse, large, terrestrial mammal group alive today Fifth largest order of mammals, consisting of 10 families, 80 genera, and approx. 210 species

therians are more closely related to __________________than monotremes

multituberculates

what are proteins made up of?

nitrogen

which ventricular septum do ancestral amniotes have?

none

molecular evidence indicates a ___________origin for eutherians as a whole

northern;

Cross-sectional area of bone does _____________ in proportion to the stress that bones experienc

not increase; Limbs of large animals are relatively more fragiles

developmental atavism

occasionally dolphins have been found that have hind flippers thought to have arisen from one or more mutations that turn the development of the hindlimbs back on.

Catarrhines origin timing and location

oligocene and africa molecular studies indicate split occured about 28 Ma

synapsid distinguishing character

one temporal fenestration, one temporal bar

homo sapiens

only surviving species of the tribe Hominini,originating in Africa 300 ka

Why do testicles descend?

optimal sperm production requires temperatures lower than that of rest of the body, but they don't understand why

hominid

orangutans, gorillas, chimps, humans and extinct forms more closely related to these taxa than to gibbbons and siamangs.

Typical order of reproductive events

ovulation copulation fertilization implantation gestation parturition lactation Oscar canned fruit implanting grapes probably late

the gut is an ___________free

oxygen free(anaerobic)

semiaquatic mammals adaptations

paddlike limbs dense fur coat

Pholidota

pangolins

quotations indicate?

paraphyletic groups

which ventricular septum do non-mammalian synapsids have?

partial

estrous

period of time shortly before and after ovullation

which era did endothermy evolve?

permian

Diversification does not always mean

phenotypic divergenec

Xenarthra: south american endemics

pilosa cingulata

artiodactyla key physical character

plane of symmetry of each foot passes through 3rd and 4th digits. "Even-toed ungulates" Most are foregut fermenters -astragalus facilitiates rapid locomotion

What drives continental drift?

plate tectonics

the great american interchange originated in which epoch

pliocene

hindgut fermenters are adapted to using

poor quality foods digestive speed

differentiated hypaxial muscles function

postural support of the body and ventilation of the lungs --Transversus abdominis: expiration of the lungs -- Rectus abdominis: postural support, "six-pack

Dark bars indicate ______________________-

presence in fossil records

choriovitelline placenta (enlarged yolk sac cavity)

primary site of gas and nutrient exchange lack extensive villi, weak connection to uterine lining first placental structure to appear after implantation of a fertilized egg in all therians; but it is transitory in eutherians

Gravity Pools fluids

problem for blood circulation on land

axial muscles in fish

provide simple side-to-side bending; allows for locomotion

buccal pumping

raising and lowering of the floor of the mouth draws water (or air) into and out of mouth: buccal pumping. This only works because of the distance between thee mouth and gills is short

radiation

rapid diversification over a relatively short interval of geologic time

evolutionary radiation

rapid diversification without assuming that phenotypic difference are adaptive

A hierarchical classification reflects not a mystical ordering of the universe, but a ____________ that has produced organisms with true genealogical relationships

real historical process;

metatherian urogential system

rectum splits off from the urine and birth canal creating its own opening in the body wall Didelphous Testicles outside of body wall, in front of the penis Penis generally kept within the body and serves as a urine and sperm channel only in therian mammals is the penis a conduit for urine

Costal ventilation of the lungs

reduces cutaneous water loss since skin does not have to be moist for gas exchange. Allows for longer necks

Hox genes

regulate expression of the hierarchical network of developmental genes.

Heat cannot flow rapidly _________or ________a large body through its _____________

relatively small surface;

Phylogeny

represents a hypothesisabout the evolutionary relationships among taxa; illustrated by a branching diagram (cladogram).

diapsids have what?

reptiles and birds; 2 temporal bars

zygapophysis function

resists compression and the pull of gravity; allows the spine to transfer weight of viscera to limbs --tetrapods that have permanently returned to the water have lost this

carnivore milk

resource rich. Higher in percent fat, protein, and energy content than the milk of either herbivores or omnivores

Morphology of Pinnipeds

retain zygapopyhses retain hind legs -modified and turned backwards -true seals cannot change position of hind legs and are clumsy on land

________________become inoculated with the appropriate microorganisms by _______________

rodents and lagomorphs; eating maternal feces

forgut fermentation process

rumen reticulum salivary amylase omasum abomasum

There are more species of ____________________than ____________________________ among the ungulates.

ruminant artiodactyls perissodactyl hindgut fermenters;

Hindgut fermentation process

salivary enzymes stomach small intestine caecum fermentation

Mid-Triassic importance

sauropsids replace synapsids as dominant tetrapod

skin elaborations

scales, hair, feathers, nails, beaks, horns All derived from keratin -- Fibrous protein seen only in vertebrates and found mainly in the outer skin (epidermis) of tetrapods

which animals can turn their hind legs forward

sea lions and walruses

What is the functional consequence of the evolution of the squamosal-dentary joint?

separates feeding from hearing

Synapomorphy

shared derived character

What kind of character is the astragalus?

shared derived character

bones withstand compressive forces much better than?

shearing forces;

hominoidea vs cercopithecoidea derived skeletal traits

shoulders, thorax, and hips broader than in monkeys. More curved ribs place vertebral column closer to the center of gravity -caudal vertebrae reduced to vestiges(coccyx)

Derived tetrapod fishes had most of the

skeletal features we find in ourselves today

characteristics of modern primates

skull and teeth -reduced number of teeth -reduced snout and olfactory apparatus, with most of the skull lying posterior to the orbits -presenceof post-orbital bar binocular eyes -possible adaptation to a frugivorous diet

xenarthra

sloths, anteaters, armadillos south american endemics sometimes known as edentates , but only anteaters are toothless pangolins are in the order carnivora

lever effect

small vibration in malleus generates larger vibration in stapes as this ratio decreases, sound pressure increases

Hominin derived dental traits

small, blunter canines diastema disappeared less sexual dimorphism->monogamy humans: jaws are V or U shaped, arched palate Catarrhine dental formula: 2.1.2.3/2.1.2.3

Monotremes embryo

smaller yolk sac yolk is not sufficient to sustain embryo until hatching eggs are retained in the uterus where they are nourished by maternal secretions eggs increase in size before the shell is excreted; young hatch 12-48 days after eggs laid choriovitelline membrane -fusion of the chorion and yolk membranes

Hypselodont

some mammals have molars that are ever-growing -derived trait

____________in the same genus are similar because they stem from a _______________

species; recent common ancestor;

fertilization

sperm fertilizes egg (zygote)

Which of the following is the defining characteristic of Mammaliaformes?

squamosal-dentary jaw that serves as the primary jaw joint

Surface area increases as the ...

square of the change in linear dimensions

To reduce the effect of shearing forces, bigger animals stand how?

stand more erect on straighter legs.

Which ossicles do all other derived tetrapods have?

stapes

fossil record of cetaceans

staring in the eocene of Pakiston and along the ancient Tethys Seas Progression from terrestrial forms with a full set of legs to aquatic forms with reduced and modified legs.

characteristics of fully aquatic mammals

streamlined bodies elongated spine all use blubber for insulation(subcutaneous fat) limbs converted to flippers

moose must consume?

sufficient energy and sufficient sodium aquatic plants are high in sodium but are bulkier and yield less energy

skeletomuscular system must?

support actual weight and withstand forces generated during locomotion

volume increases more rapidly than?

surface area

when linear dimensions double...

surface area quadruples --An animal 2x as tall as another has 4x as much surface area

Olecranon process on ulna symplesiomorphy or synapomorphy?

symplesiomorphy among tetrapods synapomorphy compared to fishes

Which lineage was first group of amniotes to radiate widely in terrestrial habitats?

synapsid lineage

To the early Permian to into the early Triassic, which lineage was the top carnivores in the food web?

synapsids

Which group was the dominant terrestrial tetrapod before and immediately after the Permain-Triassic extinction?

synapsids

Afrotheria: molecular data indicated three other groups were related to these larger african mammals

tenrecs, golden moles, elephant shrews, and aardvark

phenotypic plasticity

the ability of an organism to change its phenotype in response to changes in the environment.

delayed ovulation

the best time for mating might not be the best time for offspring to be born, especially in seasonal enviroments

Darwinian fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Volume increases as

the cube of the change in linear dimensions

Structure of the tetrapod skeletomuscular system is sensitive to absolute body size because of?

the effects of gravity on land

The most likely phylogeny is the one requiring _______________given that any change is an unlikely event

the fewest number of character changes(most parsimonious)

epigenetics

the study of environmental influences on gene expression that occur without a DNA change

Allometry

the study of scaling, or how shape changes with size

delayed implantation

the zygote floats in the reproductive tract without implanting in the uterine wall Months-long delays: 5-7 months is common across species that do this -protective coat on zygote, seasonal, nursing young

Taxonomy

theory and practice of classifying organisms

the tympanum originated in which of the following groups

therapsid

only in _____________do the ____________________tracts have separate openings

therians alimentary and urogenital tracts

only __________have precise control over excretory processes

therians;

estrous cycle

timespan fro one period of estrus to the next -monoestrous: one cycle per year (canids) -polyestrous multiple cycles per year (rodents, rabbits, hares)

Excreting urea is an ancestral character of amniotes true or false?

true

Lactation is thought to have evolved before precise occlusion and diphyodonty because (a) precise occlusion cannot develop until jaws reach adult size, and (b) an animal can only be diphyodont only if it is fed milk during it early life

true

The loop of Henle is a derived character of mammals true or false?

true

the ability to suckle is a uniquely mammalian trait

true

eutherian urogenital system

twin vaginas fuse to become one; paired uteri fuse to varying degrees penis typically outside body wall, but often sheathed agianst the belly/abdomen most males "drop"testicles behind the penis most males develop a bone in the penus(baculum) which lends support during mating

sister groups

two monophyletic groups that are each other''s closest relatives

closest living relatives of cetaceans?

ungulates

young_________typically consume soil to obtain their microorganisms

ungulates

in male therians, urine and sperm both exit the

urethra; in other male amniotes the penis is used only for sperm transmission

Mammalian urogenital tracts

urinary alimentary reproductive -all three have cloaca

didelphous

uteri, oviducts, and vaginal canals are paired

Ventricular septum

venctricle divided by : fixed or temporary barrier caused by muscle contraction

retina

vertrebrate retina conains two types of cells that respond to light rods cones SWS1 and SWS2: blue/purple RH2: blue/green LWS: green/yellow/red

Marsupial disperal followed by what?

vicariant isolation

origin of the tetrapod middle ear

was not present in the earliest tetrapods it evolved independently several times in non-amniotes and sauropsids the DMME evolved independently in Prototheria and Theria -Convergent evolution?? - in each case it involved the stapes(or columella), tympanum, and inner ear -Hyomandibula(now technically the stapes) detaches from the hyoid arch and may have controlled passage of air through the spiracle

deer are more closely related to horses or whales?

whales

lympathic system immune function:

white blood cells(macrophages) travel lymph vessels

Vertebrates have what with embryo?

yolk sac food source; shrinks over time

precocial

young born in a relatively developed state no monotremes or marsupials some placentals

altricial

young born or hatched very immature or helpless all monotremes and marsupials some placentals

implantation

zygote implants in uterine wall

Basic principles of acoustics

• A sound wave traveling in a medium of certain physical properties, namely density and elasticity, will not pass readily into a medium with different properties • The more different the characteristics of the two media are, the more sound energy will be reflected at the boundary

diaphragm

• Ancestrally, contraction of the trunk muscles created the reduced pressure with the thorax that draws air into the lungs for inspiration. • But this situation was modified with the development of a diaphragm in mammals, possibly as early as in some derived therapsids.

key disadvantage of amniotic egg?

• Eggs cannot be laid in water because the embryo bypassess the larval stage typical of amphibian embryos and does not form gills. - Gill-less embryo would drown •Marine amniotes must lay eggs on land or bear live young (viviparous)

synapsid(aveolar) lung

• Elaboration of earliest tetrapod lung • Tidal ventilation (in-and-out airflow) • Mixture of fresh air & retained air • Treelike pattern of branching - Humans: 23 levels • Alveoli are tiny & thin-walled - Thin blood-gas barrier • Extensive surface area - Humans: 70-m2

What's the advantage of changed musculature?

• Enhanced feeding ability • Fishes and non-amniotic tetrapods can only close their jaws with a single snap (inertial feeding) • Amniotes can also apply pressure with teeth when jaws closed (static pressure feeding)

Which selective pressures might have triggered the origin of tympanic hearing in synapsids?

• Non-burrowing, nocturnal lifestyle: • Finding food • Avoiding predators • Communicating with conspecifics • Upright posture: • Diminished contact between skull and substrate

lymphatic system

• One-way system of blind-ended, veinlike vessels that parallel the veins. • Allows fluid to drain back into the venous system at the base of the neck .• Valves prevent backflow • Muscle/tissue contractions maintain flow

Key advantage of a longer neck

• Provides space for elaboration of the nerves that supply the forelimb • These nerves leave the spinal cord at the neck and join together in a nerve complex called the brachial plexus • Simple plexus in amphibians (2 nerves), complex plexus in amniotes (>5 nerves) • Improves limb control and manipulation

Potential Effects of Mesozoic O2 Bottleneck for the Evolution of Synapsids

• Small body size • Enucleate Red Blood Cells - No nucleus; more oxygen-carrying hemoglobin molecules can be packed into each cell.

Sauropsid (Faveolar) Lung

• Through-flow ventilation • Air passages on the periphery of lung • Gas exchange occurs in faveoli • Air flows one way, blood flows in opposite direction (cross-current exchange) • Air flow is UNIDIRECTIONAL • Birds: Lungs relatively immobile - Parabronchi walls extremely thin - Thinner blood-gas barrier than mammals

Ancestral tetrapod lung

• Tidal ventilation(in-and-out airflow) • Mixture of fresh inhaled air & retained air from previous breaths • Limited surface area • Surfactant substance reduces water tension, helps re-inflate lung

Role of Contingency

•Evolutionary history depends on whether a particular lineage of animals was in the right place at the right time •Effects of continental movements on (a) climate, (b) isolation of animals, and (c) dispersal of animals are key drivers of mammal evolution