Overview of Animals

Overview of Animals

• All animals are multicellular eukaryotes
• No cell walls
• Collagen: protein holds bodies and tissues together
• Tissues: Group of cells that function together to perform a specific task
• Unique animal tissues: Nervous Tissue and Muscle Tissue
• All chemoheterotrophic (get energy by breaking down other cells)
• Sexual reproduction
• motile haploid sperm
• non-motile haploid egg
• Egg is much larger than sperm

Reproduction and Embryonic Development

• Most animals show similar embryonic development
• Cleavage: diploid zygote goes through mitotic cell divisions
• Blastula: Multicellular ball of cells
• Blastula is hollow, the center cavity is called the Blastocoel
• Gastrulation: forms the Gastrula
• Gastrula contains different layers of tissue
• Animal development
• Direct: embryo to adult form directly
• Indirect: develops in stages Example: Frogs, moths, butterflies

Cell Structure and Specialization

Eumetozoa

• Eumetozoa = "True Animals"
• All animals except for sponges

Body Plans

• Symmetry
• Radial: No front/back or left/right Example: Sea Star, Sea Urchin
• Bilateral: Has a left and right side, both sides are mirrored across the center line (chiral)
• Typically active movement
• Have Central Nervous System (CNS)
• Have directionality:
• left / right
• dorsal / ventral (bottom / top)
• posterior / anterior (back / front) Example: Humans, dogs, squid etc.
• Cephalization: development of a head (or CNS)

Embryonic Development

• Protostomia: First fold becomes the mouth
• Dueterostomia: Second fold becomes the mouth

Cell cleavage

• Protostomes: New cells develop in spiral pattern = Spiral Cleavage
• Determinant cells: Cells are already differentiated and WILL become a part of the embryo's body plan
• If you remove one cell, the embryo will be missing that body part
• Deuterosomes: New cells develop in radial pattern = Radial Cleavage
• Indeterminate cells: Call are NOT differentiated.
• Cells can be split / removed and embryo will make more

Germ Layer

• The development of tissues
• 3 types of tissue layers
• Endo: "inner" gastrointestinal tract (GI tract)
• Meso: "middle" muscles and organs
• Ecto: "outer" outer protection (skin, nerves)
• Radiata: only 2 cell layer
• Diploblastic
• Endo and Ecto (missing the Meso layer)
• Bilateria: 3 cell layers
• Triploblastic
• Endo, Meso and Ecto