An Introduction to Animal Structure and Function

1. An Introduction to Animal Structure and Function

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

3. 2 types of cells • Prokaryotic • Eukaryotic

4. Structural evidence that supports relatedness of all eukaryotes (at cellular level):membrane-bound organelleslinear chromosomesendomembrane system

5. Reproduction • Most animals reproduce sexually • Diploid stage dominating the life cycle

6. Development • Sperm fertilizes egg zygote cleavage blastula gastrulation formation of embryonic tissue layers gastrula

7. In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula, a hollow ball of cells. Only one cleavage stage–the eight-cell embryo–is shown here. The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage. 2 3 1 Blastocoel Cleavage Cleavage The endoderm of the archenteron de- velops into the tissue lining the animal’s digestive tract. 6 Cross section of blastula Eight-cell stage Blastula Zygote Blastocoel Endoderm The blind pouch formed by gastru- lation, called the archenteron, opens to the outside via the blastopore. 5 Ectoderm Gastrulation Gastrula Blastopore 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 Early embryonic development in animals Figure 32.2

8. Hox genes regulate development of body form • Hox family of genes has been highly conserved, yet produces a wide diversity of animal morphology

9. 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

10. Invertebrates

11. Figure 33.1 Life Without a Backbone • Invertebrates account for 95% of known animal species

12. Porifera Cnidaria Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate Figure 33.2 Animal phylogeny

13. Dorsal,hollownerve cord Brain Notochord Musclesegments Mouth Anus Pharyngealslits or clefts Muscular,post-anal tail Figure 34.3 Derived Characters of Chordates • Some species possess some of these traits only during embryonic development

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

16. Bonessupportinggills Tetrapodlimbskeleton Figure 34.19 Origin of Tetrapods • The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life in one line

19. 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. Allantois. The allantois is a disposal sac for certain metabolic wastes pro- duced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ. Extraembryonic membranes 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”). Amnion. The amnion protectsthe embryo in a fluid-filled cavity that cushions againstmechanical shock. Embryo Amniotic cavitywith amniotic fluid Yolk (nutrients) Albumen Shell Figure 34.24 Amniotic egg • 4 extraembryonic membranes

20. Wing claw Toothed beak Airfoil wing with contour feathers Long tail with many vertebrae Figure 34.29 Archaeopteryx • Oldest bird known

21. Marsupial mammals Eutherian mammals Plantigale Deer mouse Mole Marsupial mole Sugar glider Flying squirrel Wombat Woodchuck Wolverine Tasmanian devil Patagonian cavy Kangaroo Figure 34.35 Australian convergent evolution

22. Animal Form and Function

23. Figure 40.1 Structure and function * are closely correlated

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

25. Evolutionary convergence • Independent adaptation to a similar environmental challenge * (a) Tuna (b) Shark (c) Penguin (d) Dolphin Figure 40.2a–e (e) Seal

26. Exchange with the Environment • Occurs as substances dissolved in the aqueous medium transported across membranes *

27. 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

28. Organisms with complex body plans highly folded internal surfaces * (lg. surface area) specialized for exchanging materials

29. * External environment Food CO2 O2 Mouth Animal body Respiratory system Blood 50 µm 0.5 cm 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). Cells Heart Circulatory system Nutrients 10 µm Interstitial fluid Digestive system Excretory system The lining of the small intestine, a diges- tive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, 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). Anus Unabsorbed matter (feces) Metabolic waste products (urine) Figure 40.4

30. Electron shuttles span membrane MITOCHONDRION CYTOSOL 2 NADH or 2 FADH2 2 NADH 2 NADH 2 FADH2 6 NADH Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA 2 Pyruvate Glucose + 2 ATP + 2 ATP + about 32 or 34 ATP by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol by substrate-level phosphorylation by substrate-level phosphorylation About 36 or 38 ATP Maximum per glucose: Figure 9.16 Cellular respiration

31. Capillary 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. 1 Excretory tubule Filtrate 2 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. 3 Excretion. The filtrate leaves the system and the body. 4 Urine Excretory Processes • Urine produced by refining a filtrate derived from body fluids Figure 44.9

32. Posterior vena cava Renal artery and vein Kidney Aorta Ureter Urinary bladder Urethra (a) Excretory organs and major associated blood vessels Vertebrate Kidney Figure 44.13a

33. Cortical nephron Juxta- medullary nephron Afferent arteriole from renal artery Glomerulus Bowman’s capsule Renal cortex Proximal tubule Peritubularcapillaries Collecting duct SEM 20 µm Distal tubule Efferent arteriole from glomerulus Renal medulla To renal pelvis Collecting duct Branch of renal vein Descending limb Loop of Henle Ascending limb Vasarecta (d) Filtrate and blood flow (c) Nephron Nephron Figure 44.13c, d

34. Glomerulus of Bowman’s capsule proximal tubule the loop of Henle distal tubule collecting duct

35. Distal tubule Proximal tubule 4 1 Nutrients NaCl H2O HCO3 H2O K+ NaCl HCO3 NH3 H+ K+ H+ CORTEX Descending limb of loop of Henle 2 Thick segment of ascending limb 3 Filtrate H2O Salts (NaCl and others) HCO3– H+ Urea Glucose; amino acids Some drugs NaCl H2O OUTER MEDULLA NaCl Collecting duct Thin segment of ascending limb 3 5 Urea Key Active transport NaCl H2O Passive transport INNER MEDULLA Filtrate becomes urine Figure 44.14

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

37. Osmoreceptors in hypothalamus Thirst Hypothalamus Drinking reduces blood osmolarity to set point ADH Increased permeability Pituitary gland Distal tubule H2O reab- sorption helps prevent further osmolarity increase STIMULUS: The release of ADH is triggered when osmo- receptor cells in the hypothalamus detect an increase in the osmolarity of the blood Collecting duct Homeostasis: Blood osmolarity Antidiuretic hormone (ADH) • Increases water reabsorption in the distal tubules and collecting ducts (a) Antidiuretic hormone (ADH) enhances fluid retention by makingthe kidneys reclaim more water. Figure 44.16a