1. Introduction to Animals
I.   Characteristics of Animals
General Features:
    heterotrophs – cannot make their
own food
2. mobility – able to perform rapid,
complex movements

2. 3.    multicellular – made of many cells
4.    diploid – adults have 2 copies of
each chromosome, only gametes are
haploid; advantage is diversity
5. sexual reproduction – almost all
animals reproduce sexually by
producing gametes

3. 6. blastula formation – except for sponges, the zygote (fertilized egg) undergoes cell divisions that form a hollow ball of cells; eventually they develop into 3 distinct layers (ectoderm, endoderm, mesoderm)
7. cells organized into tissues – except for
sponges
8. absence of cell wall

4. Blastula Formation

5. Development of Tissues:

6. Body Plan
*term used to describe an animal’s shape, symmetry, & internal organization
1. asymmetrical – irregular shape ex. sponges
  2. radial symmetry – body parts are arranged around a central axis ex. sea anemone, starfish
3. bilateral symmetry – a body design in which there are distinct right & left halves; most bilateral symmetrical animals have evolved an anterior concentration of sensory structures and nerves through a process called cephalization.

7. Types of Body Plans
Asymmetry

8. Internal Body Cavity 1. coelom – a fluid filled space between the
body and the digestive tract
2. acoelomates – has no body cavity; its
space is filled with tissues
3. pseudocoelomates – a false cavity; a
body cavity located between the
mesoderm and endoderm

9. Body Cavities
Flatworm
Roundworm
Segment Worm

10. II. Animal Body Systems
*Complex animals have evolved tissues & organs that
are specialized to perform specific functions.
 Six Important Functions of these
Tissues and Organs Are:
1. digestion – gastrovascular cavity has one opening
digestive tract has 2 openings
2. respiration – the uptake of O2 and release of CO2
ex: skin, gills, lungs

11. 3. circulatory systems – open circulatory system (blood flows through vessels that empty into body cavities); closed circulatory system (blood flows through vessels and diffuses across the walls of vessels)
4. nervous system - conduction of nerve impulses; nerve cells (neuron) carries messages in the form of electrical impulses (conduction)

12. 5. support – hydrostatic skeleton (water contained under pressure in a closed cavity ex: hydra, sponges), exoskeleton (outside skeleton), endoskeleton (inside skeleton)
6. excretion – removal of wastes produced by cellular metabolism ex: diffusion, gills, kidneys

13. Digestive Body Systems

14. Open vs. Closed Circulatory Systems
Invertebrates
Vertebrates

15. Support
Exoskeleton
HydrostaticSkeleton
Endoskeleton

16. Reproductive Strategies
1. asexual reproduction – does not involve the fusion of 2 gametes ex: fragmentation – splitting in two, parthogenesis ( a new individual develops from an unfertilized egg ex: insects such as queen bees, some fishes and amphibians)
2. sexual reproduction – a new individual is formed by the union of a male and female gamete
external fertilization – egg is fertilized outside the female body; water is needed for fertilization to occur; seen in aquatic animals
internal fertilization – the union of eggs and sperm occurs within the female’s body; are often terrestrial (land) animals

17. hermaphrodites – a species that has both testes & ovaries ex: slugs, earthworms, some fishes
advantage: it increases the chances of reproductive success in animals that rarely meet members of their own species

18. Body Cavities