What is an Animal?

Characteristics of Animals

• All animals have several characteristics in common. What are the four common characteristics of animals?– Eukaryotic– Multicellular– Heterotrophic– No cell wall

What Do Animals Do to Survive?

• Feeding• Respiration• Circulation• Excretion• Response• Movement• Reproduction

Trends in Animal Evolution

• Your survey of the animal kingdom will begin with simple forms and move through more complicated ones.

Phylogenetic relationships: Trends in Animal Evolution

Cell Specialization and Levels of Organization

• Groups of specialized cells that work together form tissues.

• Tissues join together to form organs.

• Group of organs work together to form organ systems– EX: Circulatory

system

Cephalization

• Concentration of sense organs and nerve cells at the front end or head of the body.

Animal Body Plans

• What is symmetry? Arrangement of body parts on opposite sides of a plane or line

Asymmetry Radial Symmetry Bilateral Symmetry

Animal Body Plans

• Acoelom – Without a body cavity

Animal Body Plans

• Pseudocoelom– Fluid-filled internal

space that is in direct contact with the wall of the digestive tract.

Animal Body Plans

• Coelom– Fluid-filled body

cavity completely lined by a layer of mesoderm cells and suspending internal organs

Animal Body Plans

How do these body plans develop?

Early Development

Development of Animal Body Plans• Cell Division– The zygote divides by mitosis and cell division to

form two cells in a process called cleavage. – How important is this first cell division?• Problems can led to defects in embryo

Zygote

Development of Animals: Gastrulation (a process of forming cell layers)

• The zygote undergoes a series of divisions to form a blastula, which is a hollow ball of cells.

Demo Phylums Porifera and Cnidaria only have two layers

Protostome vs. deuterostomeMouth is formed from the blastopore Anus is formed from the blastopore

Formation of a Coelom (body cavity): Neurulation

• Body cavity – a fluid-filled space that lies between the digestive tract and the body wall.

Gastrula

Embryo Development