1. Introduction to the Animal Kingdom

2. Introduction to the Animal Kingdom
Animals are multicellular eukaryotic heterotroph whose cells lack cell walls, digestion is internal
Vertebrates: 5% of animal species with backbones
Invertebrates: 95% of animal species WITHOUT backbones
Cell specialization – special shape, physical structure, and chemical composition to perform a special function in a multicellular organism (Division of Labor)

3. Early Development
Zygote (fertilized egg) undergoes divisions to form blastula, or a hollow ball of cells
Blastula flattens on one side and folds into itself forming a single opening called a blastopore
Blastopore leads into center tube running the length of the developing embryo. This tube becomes the digestive track
Protostome – mouth formed first from blastopore (most invertebrates)
Deuterostome – anus formed first from blastopore (echinoderms and all vertebrates)

4. Early Development (continued)
Cells then differentiate into three layers, called germ layers
Endoderm – innermost germ layer – forms linings of digestive track and respiratory system
Mesoderm – middle germ layer – forms muscles, circulatory, reproductive, and excretory systems
Ectoderm – outermost germ layer – forms sense organs, nerves, and outer layer of skin

5. Early Development (continued)

6. In Order to Survive, Animals Must:
Feed –
Carnivores – eat other animals
Herbivores – eat plants
Omnivores – eat other animals and plants
Parasites – inside or on other organisms and do them harm
Filter feeders – strain food from water
Detritus feeders – feed on dead organic matter

7. In Order to Survive, Animals Must:
Respire –
Consume oxygen and give off CO2
Skin, gills, lungs

8. In Order to Survive, Animals Must:
Circulate/Internal Transport –
Must carry O2, nutrients and waste products to and from internal cells
Heart and blood vessels in larger animals
Smaller animals rely on diffusion

9. In Order to Survive, Animals Must:
Excrete –
Small animals – diffusion
Larger animals – excretory systems (that can include complex kidneys)

10. In Order to Survive, Animals Must:
Respond –
Nerve cells – brain
Gather information from environment
Varies greatly from phylum to phylum

11. In Order to Survive, Animals Must:
Move –
Sessile – one spot, no movement
Motile – move, muscles and/or skeletons

12. In Order to Survive, Animals Must:
Reproduce –
Mainly sexual, but invertebrates can also reproduce asexually
Live birth or eggs
Direct Metamorphosis – young look like adult
Indirect Metamorphosis – young → metamorphosis → adult

13. Direct Metamorphosis
Direct – young look like adult

14. Indirect Metamorphosis
Indirect – young → metamorphosis → adult

15. Early Animals and the Cambrian Explosion
Scientists hypothesize that animals evolved from a colonial flagellated protist.
The oldest animal fossils found are 550–575 million years old.
The molecular data suggest a much earlier origin for animals.

16. Early Animals and the Cambrian Explosion
Animal diversification appears to have accelerated rapidly from million years ago, during the Cambrian period.
Because so many animal body plans and new phyla appear in the fossils from such an evolutionarily short time span, biologists call this episode the Cambrian explosion.

17. Early Animals and the Cambrian Explosion
The Cambrian explosion may have been ignited by
increasingly complex predator-prey relationships and/or
an increase in atmospheric oxygen.
The genetic framework for complex bodies, a set of “master control” genes, was already in place.

18. Animal Evolution
Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end, or head, with sense organs, and a body cavity.

19. Cell Specialization Cell → tissue → organ → organ system → organism
Ex. Stomach cell → stomach tissue → digestive system (mouth, stomach, intestines, etc) → all organ systems put together

20. Body Symmetry Asymmetrical – no symmetry (sponges)
Radial symmetry – body parts repeat around center of body (simple animals – sea anemone and starfish)
Bilateral symmetry – body can be divided into two equal halves – left and right sides
Anterior – front end
Posterior – back end
Dorsal – upper side
Ventral – lower side

21. Body Symmetry Bilateral Symmetry Radial Symmetry Posterior end
Dorsal side
Anterior end
Plane of symmetry
Planes of symmetry

22. Body Cavity
Animals also vary according to the presence and type of body cavity, a fluid-filled space separating the digestive tract from the outer body wall.
There are differences in how the body cavity develops.
If the body cavity is not completely lined by tissue derived from mesoderm, it is called a pseudocoelom.
A true coelom is completely lined by tissue derived from mesoderm.

23. Body Cavity (a) No body cavity (b) Pseudocoelom (c) True coelom
Body covering
Tissue-filled region
Digestive tract
(a) No body cavity
Body covering
Coelom
Muscle layer
Body covering
Pseudo- coelom
Digestive tract
Tissue layer lining coelom and suspending internal organs
Digestive tract
(b) Pseudocoelom
(c) True coelom

24. Cephalization
Complex animals concentrate sense organs and nerve cells in the anterior end of the body, this is called cephalization
Ganglia – small clusters of nerve cells (simple animals)
Brain – clusters of ganglia (more complex animals)

25. Introduction to Invertebrates