Notes - Chapter 28

General Features of Animals

1. heterotrophy
2. mobility
3. multicellularity
4. diploidy (adults have two copies of chromosomes)
5. sexual reproduction
6. absence of a cell wall
7. blastula formation
8. tissues

Blastula Formation

Blastula - hollow ball of cells that forms after fertilization
Gastrula - the blastula pinches inward, zygote is now an embryo

The blastula develops 3 distinct layers, which become layers in the organism

1. ectoderm - outer layer of skin, nervous tissue, sense organs
2. endoderm - lining of digestive tract, digestive and respiratory system
3. mesoderm - skeleton, muscles, excretory system

Body Symmetry - the body plan of an animal, how its parts are arranged Asymmetry - no pattern (corals, sponges) Radial Symmetry - shaped like a wheel (starfish, hydra, jellyfish) Bilateral Symmetry - has a right and left side (humans, insects, cats, etc) Cephalization - an anterior concentration of sense organs (to have a head) Sides of the bilateral symmetrical animal:

anterior - toward the head posterior - toward the tail dorsal - back side ventral - belly side

Coelom - body cavity, where many organs are housed (see fig 28.10)
Segmentation - "advanced" animals have body segments, and specialization of tissue (even humans are segmented, look at the ribs and spine)

Types of Animals

Animal Body Systems

Digestion

Gastrovascular cavity - one opening
Digestive tract (gut)- two openings (one for food intake, one for waste expelling)

Respiration - taking in oxygen, releasing carbon dioxide

Diffusion across moist surfaces (earthworm)
Gills in aquatic animals
Lungs in terretrial animals

Circulation - how oxygen and nutrients are transported throughout body

Open Circulatory System - some vessels, body cavity is "washed" with blood
Closed Circulatory System - all blood is enclosed in vessels, capillaries deliver to organs

Nervous System - coordinates the activities of the animal body

Neurons - nerve cells that send impulses

Nerve Net - network of neurons, very little coordination
Ganglion - clusters of neurons (simple brain)
Brain - sensory structures and neurons located at anterior end, complex coordination and behavior

Support -how the body maintains its shape

Hydrostatic skeleton - water pressure (jellyfish, worms)
Exoskeleton - outside skeleton (insects and crabs)
Endoskeleton - inside skeleton (vertebrates)

Excretion - the removal of wastes from the body

Diffusion can release wastes in simple aquatic animals
Excretory system in terrestrial animals removes waste without loss of water

Reproduction - process by which organisms make more of their own kind

Asexual reproduction - reproduction only needs 1 parent, offspring are identical

regeneration - fragmentation and regrowth (sponges)
budding - growth of a clone and release (hydra)
parthenogenesis - rare, individual develops from unfertilized eggs

Sexual reproduction - reproduction involves the joining of egg and sperm (2 parents)

Hermaphrodite - animals that produce both egg & sperm, have both sexes (earthworm)

External Fertilization - sperm is released into water where it fertilizes eggs in the water
Internal Fertilization - sperm and egg join within the body of the female