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

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

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

Blastula Formation

Development of Tissues:

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.

Types of Body Plans Asymmetry

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

Body Cavities Flatworm Roundworm Segment Worm

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

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)

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

Digestive Body Systems

Open vs. Closed Circulatory Systems Invertebrates Vertebrates

Support Exoskeleton HydrostaticSkeleton Endoskeleton

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

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

Body Cavities