1. Chapter 32 – Animal Diversity

2. Key Concepts
Animals are multicellular, heterotrophic eukaryotes with tissue that develop from embryonic layers.
Animal history spans more than ½ billion years.
Animals can be characterized by Body Plans.
Changes in animal phylogeny are emerging from molecular data.

3. Animals differ from plants and fungi in their
Nutritional Modes
Animals differ from plants and fungi in their
mode of nutrition.
Plants are autotrophs: generate organic molecules through photosynthesis.
Fungi are heterotrophs: absorb organic molecules by growing on or near food. (digestive enzymes – produced outside body)
Animals are heterotrophs: ingest organic molecules; living and non-living. (digestive enzymes – produced inside body)

4. Cell Structure Animals are multicellular eukaryotes.
They lack structural support from cell walls, but are held together with structural proteins and collagen.
Collagen is specific to animals; its not found in plants or fungi. (most abundant protein in animal K.)
Animals also have muscle and nerve cells, not seen in other multicellular organisms.
These qualities are central to what it means to be an animal.
Collagen is the most abundant protein in the animal kingdom. Mainly found in connective tissue and bone.
It is the muscle and nerve cells that allow for many of the adaptations that differentiate animals from plants and fungi. In other words these structures are central to what it means to be an animal.

5. Animal Embryonic Development
Cleavage: succession of mitotic cell divisions without cell growth – forms a blastula (hollow ball is multi-cellular).
Cleavage
Cleavage
Blastula
Zygote
Eight-cell stage
Cross section
of blastula

6. Zygote
Gastrulation
Cleavage
Eight-cell
stage
Cleavage
Blastocoel
Cross section
of blastula
Blastula
Figure Early embryonic development in animals (step 3)
Gastrulation
The next phase of formation is the gastrula. Where layers of embryonic tissue will eventually turn into body parts.
Cross section
of gastrula
Blastocoel
Endoderm
Ectoderm
Blastopore
Archenteron

7. Zygote – Cleavage – Blastula – Gastrula
Blastocoel
Archenteron
Endoderm
Cleavage
Cleavage
Blastula
Ectoderm
Zygote
Eight-cell stage
Gastrulation
Gastrula
Cross section
Blastopore
Takes place before cells develop into the different body Parts.
Cross section
of blastula

8. Animal Growth & Progression
In addition to mitotic cell division; many organisms also (ie. macro inverts.) have a Larval Stage.
Sexually immature stage; morphologically distinct from the adult.
Animals in their larval stage tend to eat different food, and have different behaviors than a sexually mature adult.
Undergo metamorphosis; juvenile animal that resembles the sexually mature adult.

9. Animal History
The animal kingdom includes a great diversity of living species.
As well as an even larger diversity of extinct species. Possibly 99% of all animals sp.
Some studies suggest animals diverged from ancestors of fungi a billion years ago.
Others suggest a common protist; lived between million years ago.
Earth is approximately 4.5 billion years old.

10. Researchers have also hypothesized that the common ancestor of living animals may have been a stationary feeder similar to present day choanoflagellates.
Individual
choanoflagellate
Choanoflagellates
OTHER
EUKARYOTES
Sponges
KO-an-O-cyte.
Animals
Collar cell
(choanocyte)
Other animals

11. Animal Evolution
There is fossil evidence that animals have evolved from distant ancestors over four geologic eras:
Neoproterozoic (1 Billion m.y.a.)
Paleozoic ( m.y.a.)
Mesozoic ( m.y.a.)
Cenozoic (65.5 m.y.a.)

12. Neoproterozoic Era
The first macroscopic fossils of animals are dated to approximately 550 million years old.
Multicellular eukaryotes known from Australia; Ediacaran biota ~ soft body mulluscs, snails, and possible relatives of sponges and anemones.
In general the fossil record suggests : the end of the Neoproterozoic era was a time of increasing animal diversity.
Older fossils may still be found, but at this point china and australia have the oldest recorded fossils.

13. (a) Mawsonites spriggi (b) Spriggina floundersi
Fig. 4
1.5 cm
0.4 cm
Fossils with radial symmetry and segmented bodies.
(a) Mawsonites spriggi
(b) Spriggina floundersi

14. Paleozoic Era (542-251 million)
Dramatic acceleration of animal diversity during the Cambrian era which was m.y.a.
Cambrian explosion! Precambrian strata has only a few animal phyla in comparison.
Approximately half of all extinct animal phyla are found in these rock layers.
first arthopods,
then cordates,
and echinoderms
Several hypotheses are have emerged as to why…

15. Fig. 5
Cambian landscape

16. Cambrian Explosion Theories
New predator-prey relationships were created through natural selection.
- Predators acquired better locomotion
- Prey acquired protective shells.
Oxygen Levels increased dramatically preceding the Cambrian explosion.
- Animals with higher metabolic rates and larger body sizes thrive.

17. 3) Hox gene complex allowed for developmental flexibility that resulted in morphologic variations.
These hypotheses are not exclusive – they all may have played a role in animal diversity.

18. Diversified into numerous terrestrial groups.
Toward the end of the Paleozoic era animal diversity continued to increase, but was followed by periodic episodes of extinction.
It was during this time vertebrates made the transition to land. (365 m.y.a)
Diversified into numerous terrestrial groups.
Amphibians; frogs and salamanders
Amniotes; reptiles and mammals

19. Mesozoic Era Animals spread into new ecological habitats.
- first coral reefs formed
- some reptiles returned back to the water
- winged animals evolved
- small dinosaurs emerged
More mammals, flowering plants and insects also emerged.

20. Cenozoic Era
Mass extinctions of terrestrial and marine animals. (65.5 m.y.a)
We lost large non-flying dinosaurs and many marine reptiles.
Large mammalian herbivores and predators exploited the vacated ecological niches.
Global climate was cooling. Changed behaviors (ie; primates moved to open woodlands, and savanas)

21. Body Plans A set of morphological and developmental traits.
Important to remember- similar body plans can evolve independently. (convergent evolution)
Physical constraints tend to dictate form.
Body plans => characterized by symmetry.

22. (b) Bilateral symmetry
Fig. 7
(a) Radial symmetry
Many animals have sensory equipment, and/or brains at their anterior end. An evolutionary trait called cephalization.
So which symmetry do you think leads to a more active lifestyle?
(b) Bilateral symmetry

23. Body Plans
Radial symmetry: have a top and a bottom, no front and back.
Bilateral symmetry: has a left and right, top and bottom, and cephalization (conc. sensory equip.)
Dorsal = Top
Ventral = Bottom
Anterior = Front
Posterior = Back

24. Tissue
Ectoderm – germ layer covers the outer surface of the organism. (also central nervous system)
Endoderm – germ layer lines most inner surfaces. Creating digestive tract and organs.
Animals with radial symmetry tend to be diploblastic – two layers. (Cnidarians)
Animals with bilateral symmetry are triploblastic – and have a 3rd layer.
Mesoderm – germ layer that forms the connective tissue and muscles surrounding the organs.
What would humans be?

25. Triploblastic Organisms
Coelomates: have body cavity made of mesoderm; suspends internal organs. Digestive tract is formed by endoderm.
Pseudocoelomates: have body cavity, no organs. Just a digestive tract made of mesoderm and endoderm.
Acoelomates: lack a body cavity or coelom.

26. Coelom Body covering (from ectoderm) Tissue layer lining coelom
Fig. 8a
Coelom
Body covering
(from ectoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Digestive tract
(from endoderm)
Seal – em-ates
(a) Coelomate

27. Body covering (from ectoderm) Pseudocoelom Muscle layer (from
Fig. 8b
Body covering
(from ectoderm)
Pseudocoelom
Muscle layer
(from
mesoderm)
Digestive tract
(from endoderm)
(b) Pseudocoelomate

28. Wall of digestive cavity (from endoderm)
Fig. 8c
Body covering
(from ectoderm)
Tissue-
filled region
(from
mesoderm)
Wall of digestive cavity
(from endoderm)
(c) Acoelomate

29. Divergent Development
Protostome versus Deuterostome
Development modes are distinguished by differences in cleavage, coelom forms, and fate of the blastopore.

30. Planes of cell division are diagonal to the vertical access.
Fig. 9a
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
(a) Cleavage
Eight-cell stage
Eight-cell stage
Spiral and determinate
Radial and indeterminate
Planes of cell division are diagonal to the vertical access.
Planes of cell division are parallel or perpendicular to vertical access.

31. Protostome development (examples: molluscs, annelids)
Fig. 9b
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
(b) Coelom formation
Coelom
Key
Ectoderm
Archenteron
Mesoderm
Endoderm
Coelom
Mesoderm
Blastopore
Blastopore
Mesoderm
Solid masses of mesoderm
split and form coelom.
Folds of archenteron
form coelom (outpocketing).

32. Proto = first Deuteros = second Stroma = mouth Stroma = mouth
Fig. 9c
Proto = first
Stroma = mouth
Deuteros = second
Stroma = mouth
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
(c) Fate of the blastopore
Anus
Mouth
Key
Ectoderm
Digestive tube
Mesoderm
Endoderm
Mouth
Anus
Mouth develops from blastopore.
Anus develops from blastopore.

33. Phylogenic Tree
Historic accounts of evolution have typically been based on morphologic structure.
Molecular evidence is now changing the way Clades have been traditionally organized.
DNA and RNA analysis – changing how we see ancestor relations.

34. Old World View - Based on Morphology
Fig. 10
“Porifera”
Cnidaria
ANCESTRAL
COLONIAL
FLAGELLATE
Metazoa
Ctenophora
Eumetazoa
Ectoprocta
Brachiopoda
Deuterostomia
Echinodermata
Chordata
Bilateria
Platyhelminthes
Old World View - Based on Morphology
Rotifera
Protostomia
Mollusca
Annelida
Arthropoda
Nematoda

35. Currently Accepted Phylogenic Tree