What is a mammal? Synapomorphies of Mammalia. Endothermic vertebrate Amniotic egg Four chambered heart

Mammals What is a mammal?    Endothermic vertebrate Amniotic egg Four chambered heart Synapomorphies of Mammalia         Mammary glan...
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Mammals

What is a mammal? 

 

Endothermic vertebrate Amniotic egg Four chambered heart

Synapomorphies of Mammalia        

Mammary glands Hair Three inner ear bones Neocortex region of brain Single lower jaw bone (mandible) Differentiated teeth Diphyodont dentition Two occipital condyles

Anapsids, Synapsids and Diapsids Based on number of temporal openings (fenestra) 

Orbit (eye socket)

Jaw muscle attachment

Anapsid: no temporal openings 

Turtles

Synapsid: single temporal opening 

Mammals

Diapsid: two temporal openings 

Reptiles including birds

Temporal fenestra

Evolutionary History of Mammals Mammals  

First appeared ~225 mya Small nocturnal, insectivores

Cynodonts 



First appeared ~270 mya Secondary palate

Therapsids  

First appeared ~290 mya Limbs vertically oriented

Synapsids  

First appeared ~320 mya Large herbivores and carnivores

Evolution of the Mammal Skull Synapsids   

Large temporal fenestra Differentiated teeth on single dentary bone Hinge between quadrate and articular

Therapsids 

Further differentiation of teeth 



Canines and incisors

Larger dentary bone

Cynodonts   

 

Cusped teeth Secondary palate Hinge forms between dentary and squamosal Quadrate and articular bones migrate to inner ear Single lower jaw bone (dentary)

Mammal Dentition  

Differentiation of teeth led to success in mammals Size and arrangement of teeth associated with diet 

Cusps

Four distinct tooth types  Incisors: cutting  Canines: tearing  Premolars: grinding  Molars: crushing, grinding

Diversification of Mammalian Dentition A.

Hedgehog

K.

Raccoon

B.

Mole

L.

Coyote

C.

Armadillo

M.

Mountain lion

D.

Anteater

N.

Horse

E.

Giant Anteater

O.

Deer

F.

Marmoset

P.

Jackrabbit

G.

Peccary

Q.

Woodrat

H.

Bear

R.

Porpoise

I.

Fruit-eating bat

S.

Right whale

J.

Nectar-eating bat

T.

Walrus

Digestive Tracts of Carnivores and Herbivores Carnivores 

Large, expandable stomachs

Herbivores 

Large cecum with symbiotic bacteria break down plant material

Modes of Locomotion

Plantigrade   

Most ambulatory (walking) mammals Walk on soles of hands and feet Bears, primates, lagomorphs

Digitigrade   

Many cursorial (running) mammals Run on one or more toes Canids, felines

Unguligrade   

Ungulates Walk or run on hoofs (nails) Horses, pigs, camels

Marsupials  

Dependency on yolk sac for nutrition Young born in very immature state  

Short gestation period Prolonged lactation period

Eutherians  

Placenta facilitates nutrient transfer between embryo and mother Young born in well developed state 



Long gestation period Short lactation period

Days after conception

Lactation versus Gestation Times 500

Gestation 400

Lactation

300 200 100 0 Grasshopper mouse

Marsupial mouse

Thomson's gazelle

Wallaroo

Lactation Lactation: secretion of milk from mammary glands   

Modified sweat glands Prolactin: stimulates milk production Oxytocin: stimulates milk delivery

Milk: nutritional liquid comprised of fats, proteins, and lactose   

Nutrition for newborn Transmits passive immunity Supports growth of intestinal flora

Major Lineages of Mammals 

Monotremes    



Lack a placenta Leathery eggs similar to reptiles True cloaca Body temp ~ 32°C

Marsupials 

Rudimentary, short lived placenta 

 



Monotremes

Short gestation period

External cloaca only Body temp ~ 35°C

Eutharians   

Placenta Separate urinary, fecal and reproductive openings Body temp ~ 38°C

Marsupials

Lactation, hair

Live birth, nipples,

Eutherians Well-developed placenta, separate reproductive, urinary, and fecal openings

Major lineages of Mammals Monotremes 

Lack a placenta 



Leathery eggs similar to reptiles

Body temp ~ 32°C

Marsupials Rudimentary, yolk sac placenta  Body temp ~ 35°C 

Platypus, echidnas Marsupials

Golden moles Elephant shrews Aardvarks Elephants Hyrax Manatees Armadillos, sloths, anteaters Flying lemurs Tree shrews Apes, monkeys, humans Rabbits and hares Rodents

Eutharians Well-developed placenta  Body temp ~ 38°C 

Hedgehogs, moles, true shrews

Canines, felines, bears, seals, weasels Pangolins Horses, tapirs, rhinos Camels, pigs, whales, dolphins, antelope Bats

Mammal Reproductive Tracts

Monotremes

Marsupials

Eutherians

Monotremes 



Prototherians (“first wild beast”) Single platypus species and four species of echidna 

All found in either Australia or Papua New Guinea 



Milk glands 

   



Lack nipples

Egg laying Lack teeth as adults Reptile like gate Low metabolic rate 



Gondwana

Body temp. ~32°C

Single vagina, two uteri Cloaca 

Single opening similar to reptiles

Marsupials 

 

Limited to Australia and the Americas Yolk sac placenta High metabolic rate 

 

Marsupium (pouch) often present Scrotum anterior to penis 





No baculum

Females have bifurcated reproductive tract 



Body temp. ~35°C

Three vagina and two uteri

Male penis bifurcated at tip Small braincase (relative to body size) 



Minimal neocortex development No corpus callosum

Eutherians 

Worldwide distribution 



Scrotum posterior to penis 



One vagina with uterus

High metabolic rate 



Baculum sometimes present

Female have single reproductive tract 



Introduced to Australia

Body temp ~38°C

Large braincase (relative to body size) 



Neocortex

Complex neocortex: higher functions including sensory perception, language, spatial reasoning, motor commands Corpus callosum: connects left and right hemispheres of brain

Corpus callosum

Differences in the Placenta Marsupials 

 

Rudimentary connection between yolk sac and maternal tissue Large yolk sac provides nutrients to developing embryo Allantois: avascular; storage of nitrogenous waste

Eutherians 

Umbilical cord connects fetus to uterus  

 

Umbilical vein and artery Efficient exchange of nutrients, gases and waste

Reduced yolk sac Allantois connects fetal bladder to yolk sac, which drains into umbilical cord

Marsupial

Eutherian Chorion Amnion Embryo Allantois Yolk Sac Fetal portion of placenta Maternal portion of placenta

Umbilical cord

Placental Mammals Placenta: organ that connects developing fetus to uterine wall and facilitated transfer of gases, nutrients and wastes. Chorion: outermost membrane that develops chorionic villi, which facilitate exchange between mother and fetus Umbilical cord: vascularized cord connecting fetus to placenta

Biogeography of Mammals Early Jurassic (~ 200 mya) • Monotremes and marsupials in southern Pangaea

Early Cretaceous (~ 135 mya) • Marsupials and monotremes isolated in “Australia” • Marsupials isolated on “South America”

Late Jurassic (~ 180 mya) • Eutheria diverge from Marsupials in “South America”

Early Paleocene (~ 65 mya) • Dinosaurs extinct • Mammal radiation • Separation of primates • New world/old world • Lemurs • Eutheria northern distribution

Primate Evolution 

Ancestral primate (arboreal) (65 mya) 





binocular vision opposable thumb

Prosimians 

lemurs, tarsiers pottos

Primate Evolution 

Ancestral primate (arboreal) (47 mya)  



binocular vision opposable thumb

“Ida” – Missing Link 

   

No claws Lack a tooth comb Short limbs Short face Talus – corner of leg/foot

Primate Evolution 

Anthropoids (50 mya) 

Monkeys 

Old World   

External nares close together Opposable thumbs Calloused ischial tuberosities

Primate Evolution 

Anthropoids (50 mya) 

Monkeys 

New World   

Broad flat nasal septum Nonopposable thumb Prehensile tail

Primate Evolution 

Hominoids (30 mya) 

apes

Human Evolution

  





Brain Size Jaw Size Bipedalism Reduced Size difference in sexes Family Structure

Human Evolution 



Sahelanthropus (6.5 million years ago)

Human Evolution 



Laetoli Footprints (3.5 million years ago)

Human Evolution 



Australopithecus (3.24 million years ago)

Primate Evolution 

Homo genus (2.4-1.6 mya)  Homo sapiens (200,000 years ago)

Primate Evolution 

Neanderthals (40,000 years old)

Human Evolution   

Turkana Boy (Homo ergaster) (1.7 million years ago) Between H. habilis and H. erectus

Origin of Modern Humans 

Out of Africa (monogeneus) 



all races of humans evolved from an ancestor in Africa

Multiregional 

Each race evolved from regional populations of Homo erectus

Evolution of the Vertebrate Heart 

Two chambers (one atria and one ventricle) 



along with a sinus venosus and a conus venosus)

Two chambers plus septa 

lungfish

Vertebrate Excretory Systems 

Pronephros 



Mesonephros 



adult hagfish, embryonic fish, amphibians, reptiles, birds, mammals adult lamprey, fish, amphibians, embryonic reptiles, birds, mammals

Metanephros 

adult reptiles, birds, mammals

The Human Excretory System    

Kidneys Ureters Urinary Bladder Urethra

Blood Filtrate to Urine 

Bowman’s Capsule and the Glomerulus 



(filters the blood)

Proximal tubule   

reabsorbed (NaCl, Potassium, Water, Nutrients) secretes ( ammonia) regulates (pH)

Blood Filtrate to Urine 

Loop of Henle 

Descending loop 



reabsorbed (water)

Ascending loop 

reabsorbed (NaCl)

Blood Filtrate to Urine 

Distal tubule   



reabsorbed (NaCl, Water) secrete (potassium) regulate (pH)

Collecting duct 

reabsorbed (NaCl, Water, Urea)

Control of the Kidney 

Antidiuretic hormone (ADH) 



Renin-angiotensinaldosterone system (RAAS) 



water reabsorption

water reabsorption

Atrialnatiuretic Factor (ANF) 

inhibits the release of renin

Evolution of the Vertebrate Heart 

Three chambers (two atria and one ventricle) 

amphibians, reptiles

Evolution of the Vertebrate Heart 

Four chambers (two atria and two ventricles) 

Crocodilians, mammals, birds

Path of Blood Through The Heart       

Anterior and Posterior Vena Cava Right Atria Atrioventricular (AV) Valve (tricuspid) Right Ventricle Semilunar Valve Pulmonary Arteries Lungs

      

Pulmonary Veins Left Atria Atrioventricular (AV) Valve (bicuspid) Left Ventricle Semilunar Valve Aorta Body

Circulatory Schemes

Cardiac Cycle Diastole Contract

Neither

Atrial Systole Atria

Valves

AV open Semilunar closed 0.4 sec

AV open Semilunar closed 0.1 sec

Time

Function Fill Heart Overfill Ventricle

Ventricular r Systole

Ventricle AV closed Semilunar open 0.3 sec Pump Blood

Cardiac Output  

Volume of blood per minute from the left ventricle Depends on two factors  



Heart rate (pulse) Stroke volume

Average Human   

75 ml/beat 70 beats/min 5.25 L/min (your blood volume)

Cardiac Control 

Annelids and Mollusks 



Arthropods 



myogenic neurogenic

Vertebrates 

myogenic and neurogenic

Control of Heart Rhythm  

Sinoatrial node (pacemaker) Atrioventricular node

Mammalian Blood Composition 

Plasma (55%)     

 

Water Ions Plasma Proteins Nutrients Wastes Gases Hormones



Cellular Elements (45%)   

Erythrocytes Leukocytes Platelets

Blood Clotting  

Injury triggers platelets to area Changes prothrombin to thrombin which than converts fibrinogen to fibrin

Blood Pressure

 

Systolic Pressure Diastolic Pressure

Cardiovascular Disease     

 

Hypertension Heart Attack Stroke Atherosclerosis Arteriosclerosis LDL’s HDL’s

Cardiovascular “Surgeries”   

Angiogram Angioplasty Stents

Cardiovascular “Surgeries” 

Bypass Surgery

Cardiovascular Disease

Cardiovascular Disease

Ventilation Lungs 

  

  

Found in amphibians, reptiles, mammals and birds Pharynx Larynx Trachea Bronchi Bronchioles Alveoli

Alveoli

Ventilating The Lungs 

Positive Pressure Breathing 



pushes air down trachea seen in frogs and other amphibians



Negative Pressure Breathing  

suction created by diaphragm seen in mammals

Negative Pressure Breathing

Breathing Control  

Occurs in Medulla oblongota and Pons Monitors Carbon Dioxide (converts to carbonic acid) 

lowers pH and causes increase in depth and rate of breathing

Oxygen Transport

 

Hemocyanin - used by arthropods and mollusks Hemoglobin - used by verts

CO2Transport

Carbon Dioxide Transport 

Carbon dioxide transported from tissue by erythrocyte   

7% transported as Carbon Dioxide in blood 23% of Carbon Dioxide and most of the Hydrogen ions are attached to hemoglobin 70% transported as Bicarbonate in plasma

Deep-diving Mammals 

Stores large amounts of oxygen in blood and muscles (twice as much as us) 

 

twice the volume of blood huge spleen myoglobin

Deep-diving Mammals 

Conservation techniques   

exhale before diving (prevent bends / pressure) decrease heartrate and oxygen consumption reduce blood supply to muscles (anaerobic)

Overview of a Nervous System

Axons   

Myelin Sheath - insulating layer Node of Ranvier - gaps between Schwann Cells Synaptic Terminals - neuron ending

Clusters of Neurons 

Ganglion 



Cluster of nerve cell bodies in the PNS

Nuclei 

Cluster of cells in the brain

Supporting Cells 

Glia (glue) 

Astrocytes (structural support) 



Radial Glia 



Form tracks for new neurons formed in the neural tube

Oligodendrocytes 



Creates tight junctions and forms the blood-brain barrier

Form myelin sheath in brain

Schwann Cells 

Form myelin sheath in the PNS

Reflex 

Sensory neuron to a motor neuron

Neural Signals  

Membrane Potential Sodium-Potassium Pump

Threshold Potential

Resting State 



Both sodium and potassium activation gates are closed Interior of cell is negative

Depolarization State 



Sodium activation gates are opened on some channels Interior of cell becomes more positive

Rising Phase of Action Potential 



Most sodium activation gates are opened Potassium activation gates are still closed

Falling Phase of Action Potential 





Inactivation gates on sodium channels are closing Activation gates on potassium channels are opened interior of cell becomes more negative

Undershoot 





Both gates to sodium channels are closed Potassium channels are closing Membrane returns to its resting state

Propagation of the Action Potential 





Localized event First action potential’s depolarization sets off second action potential Travels in one direction due to refractory period

Salatory Conduction  

Action Potential jumps from node to node Speeds up signal from 5 m/sec to 150 m/sec

Communication Between Synapses 

Electrical Synapses 



gap junctions allow for direct transfer of action potential (used during escape responses)

Chemical Synapses 

uses neurotransmitters

Chemical Synapse

Chemical Synapses   





Action potential triggers an influx of calcium Synaptic vesicles fuse with presynaptic membrane Neurotransmitter released into synaptic cleft Neurotransmitters bind to receptors and open ion channels on postsynaptic membrane which sets off new action potential Neurotransmitters are degraded by enzymes or removed by a synaptic terminal

Neurotransmitters

Postsynaptic Potentials

Postsynaptic Potentials 

Subthreshold 



Temporal Summation 



two signals do not reach threshold level but occur close enough to set off action potential

Spatial Summation 



doesn’t reach threshold

two signals are set off at the same time setting off an action potential

Spatial Summation with an inhibitor 

doesn’t reach threshold

Vertebrate Nervous System

Central Nervous System 

Ventricles (4) 



White Matter 



Cerebrospinal fluid

Made up of axons

Gray Matter 

Made up of dendrites

Peripheral Nervous System

Peripheral Nervous System  

Autonomic Nervous System regulates the internal environment (usually involuntary) Somatic Nervous System regulates the external environment (usually voluntary)

Autonomic Nervous System

Autonomic Nervous System 

Sympathetic Division 



Flight or fight response

Parasympathetic Division 

Rest or digest response

Brain

The Brainstem 



The Medulla Oblongata and the Pons controls breathing, heart rate, digestion The Cerebellum controls coordination of movement and balance

The Midbrain 

The Midbrain receives, integrates, and projects sensory information to the forebrain

The Diencepholon 

Forebrain 

Epithalamus 



Thalamus 



Includes the pineal gland and the choroid plexus conducts information to specific areas of cerebrum

Hypothalamus 

produces hormones and regulates body temperature, hunger, thirst, sexual response, circadian rhythms

The Telencepholon 

Cerebrum 

with cortex and corpus callosum 

higher thinking

Cerebrum

Cerebrum

Cerebrum

Limbic System 

Regulates emotions 

Association with different situations is done mostly in the prefrontal lobe

Memory 

Short Term 



Done in the frontal lobe

Long Term 

Frontal lobes interact with the hippocampus and the amygdala to consolidate

Overview of a Nervous System 

Sensory Input  



Integration  



conduction of signals from sensory receptors PNS environmental information is interpreted CNS (brain and spinal cord)

Motor Output  

conduction of signals to effector cells PNS

Evolution of the Eye 

Complex eyes have developed many times

Photoreceptors 

Camera Type Eyes – Evolved several times   

Hagfish eye Lamprey eye Jawed vertebrate eyes

Single Lens Eye     

  

Sclera (white) Cornea (clear) Choroid (pigmented) Iris (color of eye) Retina (rods and cones) Pupil Fovea (focal point) Blind spot

Photoreceptors

Scars of Evolution 1. inside out retina that forces light to pass through the cell bodies and nerves before hitting the retina 2. blood vessels across the retina that cause shadows 3. nerve fibers that exit causing a blind spot

Focusing 

Near vision  



ciliary muscle contracted lens becomes more spherical

Distance vision  

ciliary muscle relaxed lens becomes flatter

Visual Problems 

Near-sightedness (myopia) 



Far-sightedness (hyperopia) 



eyeball too long / focal point in front of fovea eyeball too short / focal point behind fovea

Astigmatism (blurred vision) 

misshapen lens or cornea

Hearing and Equilibrium

Hearing Organ 

Outer Ear  



Middle Ear 





pinna and the auditory canal tympanic membrane malleus, incus and stapes oval window

Inner Ear 

cochlea with the Organ of Corti 



with a basilar membrane and hair cells

Eustachian Tube

Sound 

Volume  



amplitude of sound wave vibrates fluid in ear and bend hair cells which generates more action potentials

Pitch 

frequency of sound wave

Equilibrium  

Utricle and Saccule Semicircular Canals 

used to detect body position and movement

Chemoreception 

Taste Buds 

sweet (tip), salty (behind), sour (sides), bitter (back of tongue)

Chemoreception 

Olfactory receptors cells 

upper portion of nasal cavity