An Introduction to Animal Structure and Function

• Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers

• 2 types of cells • Prokaryotic

• Eukaryotic

Structural evidence that supports relatedness of all eukaryotes (at cellular level):

membrane-bound organelles

linear chromosomes

endomembrane system

Reproduction • Most animals reproduce sexually

• Diploid stage dominating the life cycle

Development• Sperm fertilizes egg zygote cleavage blastula

gastrulation formation of embryonic tissue layers gastrula

Zygote

Cleavage

Eight-cell stage

Cleavage

Blastula Cross section of blastula

Blastocoel

Blastocoel

Gastrula Gastrulation

Endoderm

Ectoderm

Blastopore

Early embryonic development in animals

Figure 32.2

In most animals, cleavage results in theformation of a multicellular stage called a blastula.The blastula, a hollow ball of cells.

3

The endoderm ofthe archenteron de-

velops into the tissuelining the animal’s

digestive tract.

6

The blind pouchformed by gastru-

lation, calledthe archenteron,

opens to the outsidevia the blastopore.

5

Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer).

4

Only one cleavagestage–the eight-cellembryo–is shown here.

2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage.

1

• Hox genes regulate development of body form• Hox family of genes has been highly conserved, yet

produces a wide diversity of animal morphology

Paleozoic Era (542–251 Million Years Ago)• The Cambrian explosion

• Earliest fossil appearance of many major groups of living animals

• Several current hypotheses

Figure 32.6

Invertebrates

Life Without a Backbone• Invertebrates account for 95% of known animal

species

Figure 33.1

Animal phylogeny

Ancestral colonialchoanoflagellate

Eumetazoa

Bilateria

Deuterostomia

Por

ifera

Cni

daria

Oth

er b

ilate

rians

(inc

ludi

ngN

emat

oda,

Arth

ropo

da,

Mol

lusc

a, a

nd A

nnel

ida)

Ech

inod

erm

ata

Cho

rdat

a

Figure 33.2

Derived Characters of Chordates• Some species possess some of these traits only during

embryonic development

Musclesegments

Brain

Mouth

Anus

Dorsal,hollow

nerve cord

Notochord

Muscular,post-anal tail

Pharyngealslits or clefts

Figure 34.3

Origin of Craniates• ~ 530 million years ago during the Cambrian explosion

Origin of Tetrapods• The fins became progressively more limb-like while the

rest of the body retained adaptations for aquatic life in one line

Tetrapodlimbskeleton

Bonessupportinggills

Figure 34.19

Amniotic egg• 4 extraembryonic membranes

Figure 34.24Shell

Albumen

Yolk (nutrients)

Amniotic cavitywith amniotic fluid

Embryo

Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”).

Allantois. The allantois is a disposalsac for certain metabolic wastes pro-duced by the embryo. The membraneof the allantois also functions withthe chorion as a respiratory organ.

Amnion. The amnion protectsthe embryo in a fluid-filled cavity that cushions againstmechanical shock.

Chorion. The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell.

Extraembryonic membranes

Archaeopteryx• Oldest bird known

Figure 34.29

Toothed beak

Airfoil wing with contour feathers

Long tail with many vertebrae

Wing claw

Australian convergent evolution

Figure 34.35

Marsupial mammals Eutherian mammals

Plantigale

Marsupial mole

Sugar glider

Wombat

Tasmanian devil

Kangaroo

Deer mouse

Mole

Woodchuck

Flying squirrel

Wolverine

Patagonian cavy

Animal Form and Function

Structure and function * are closely correlated

Figure 40.1

Natural selections select for what works best among the available variations in a population

*

Evolutionary convergence• Independent adaptation to a similar environmental

challenge

*

Figure 40.2a–e

(a) Tuna

(b) Shark

(c) Penguin

(d) Dolphin

(e) Seal

Exchange with the Environment

• Occurs as substances dissolved in the aqueous medium

transported across membranes *

Diffusion

(a) Single cell

• Single-celled protist has a sufficient surface area * of plasma membrane to service its entire volume of cytoplasm

Figure 40.3a

• Organisms with complex body plans highly folded

internal surfaces * (lg. surface area) specialized for exchanging materials

*External environment

Food CO2 O2Mouth

Animalbody

Respiratorysystem

Circulatorysystem

Nutrients

Excretorysystem

Digestivesystem

Heart

Blood

Cells

Interstitialfluid

Anus

Unabsorbedmatter (feces)

Metabolic wasteproducts (urine)

The lining of the small intestine, a diges-tive organ, is elaborated with fingerlikeprojections that expand the surface areafor nutrient absorption (cross-section, SEM).

A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM).

Inside a kidney is a mass of microscopic tubules that exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM).

0.5 cm

10 µm

50 µ

m

Figure 40.4

Cellular respiration

Electron shuttlesspan membrane

CYTOSOL 2 NADH

2 FADH2

2 NADH 6 NADH 2 FADH22 NADH

Glycolysis

Glucose2

Pyruvate

2AcetylCoA

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

MITOCHONDRION

by substrate-levelphosphorylation

by substrate-levelphosphorylation

by oxidative phosphorylation, dependingon which shuttle transports electronsfrom NADH in cytosol

Maximum per glucose:About

36 or 38 ATP

+ 2 ATP + 2 ATP + about 32 or 34 ATP

or

Figure 9.16

Excretory Processes• Urine produced by refining a filtrate derived from body

fluids

Figure 44.9

Filtration. The excretory tubule collects a filtrate from the blood.Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.

Reabsorption. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.

Secretion. Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.

Excretion. The filtrate leaves the system and the body.

Capillary

Excretorytubule

FiltrateU

rine

1

2

3

4

Vertebrate Kidney

Figure 44.13a

Posterior vena cava

Renal artery and vein

Aorta

Ureter

Urinary bladder

Urethra

(a) Excretory organs and major associated blood vessels

Kidney

Nephron

Figure 44.13c, d

Juxta-medullarynephron

Corticalnephron

Collectingduct

To renalpelvis

Renalcortex

Renalmedulla

20 µm

Afferentarteriolefrom renalartery Glomerulus

Bowman’s capsuleProximal tubule

Peritubularcapillaries

SEM

Efferentarteriole fromglomerulus

Branch ofrenal vein

Descendinglimb

Ascendinglimb

Loopof

Henle

Distal tubule

Collectingduct

(c) Nephron

Vasarecta

(d) Filtrate and blood flow

• Glomerulus of Bowman’s capsule proximal tubule the loop of Henle distal tubule collecting duct

Proximal tubule

Filtrate

H2OSalts (NaCl and others)HCO3

–

H+

UreaGlucose; amino acidsSome drugs

Key

Active transport

Passive transport

CORTEX

OUTERMEDULLA

INNERMEDULLA

Descending limbof loop ofHenle

Thick segmentof ascendinglimb

Thin segmentof ascendinglimb

Collectingduct

NaCl

NaCl

NaCl

Distal tubuleNaCl Nutrients

UreaH2O

NaCl

H2OH2OHCO3

K+

H+ NH3

HCO3

K+ H+

H2O

1 4

32

3 5

Filtrate becomes urine

Figure 44.14

• The mammalian kidney’s ability to conserve water is a key terrestrial adaptation

Antidiuretic hormone (ADH)• Increases water reabsorption in the distal tubules and

collecting ducts

Figure 44.16a

Osmoreceptorsin hypothalamus

Drinking reducesblood osmolarity

to set point

H2O reab-sorption helps

prevent furtherosmolarity increase

STIMULUS:The release of ADH istriggered when osmo-receptor cells in the

hypothalamus detect anincrease in the osmolarity

of the blood

Homeostasis:Blood osmolarity

Hypothalamus

ADH

Pituitarygland

Increasedpermeability

Thirst

Collecting duct

Distaltubule

(a) Antidiuretic hormone (ADH) enhances fluid retention by makingthe kidneys reclaim more water.