Biology 1112

1
Lecture 4

• Biology 1112
• Chapter 18 The Evolution of Animal Diversity

2
Learning Objectives

• Define
• Blastula
• Discuss
• Characteristics of all animals
• Evolution of animals
• Contrast
• Different kinds of body symmetry
• Polyp vs. medusa

3
Question for Discussion

• What is an animal?
• How do we define it?

4
Classifying Animals
5
Characteristics of All Animals

• Eukaryotic
• Multicellular
• Heterotrophic
• No cell walls
• Blastula

6
Animal Origins

• Probably evolved from single-celled protists
• May have arisen when dividing cells didnt
  separate

7
The Blastula

• This is a hollow ball of cells
• Develops from animal zygote (fertilized egg)
• Occurs in all animals, and no other groups
• Later, one side folds in to form gastrula

8
Hypothetical Proto-animals

• Probably formed a hollow ball of cells (similar
  to blastula)
• Later, the ball folded in, forming a double layer
• Eventually, cells began to specialize, forming
  different tissues

9
Sponges

• The phylum Porifera
• Have radial symmetry
• Several cuts could divide equally
• Three layers
• Inner
• Middle
• Outer

10
Outer Layer

• Protects the rest of the sponge
• Has pores (ventilation holes) to permit water
  movement

11
Inner Layer

• Has choanocyte cells
• They have moving cilia
• Capture food (bacteria)
• Circulate water within the sponge

12
Middle Layer

• Skeleton
• Amoebocytes
• These cells move freely between outer and inner
  layers
• Digest food, transport materials and oxygen

13
Cnidarians

• Phylum Cnidaria
• Characteristics
• Radial symmetry
• Cnidocytes
• Two Cnidarian body types
• Hydra vs. Polyp

14
Cnidarians Have Cnidocytes

• Special stinging cells
• Have tiny barbs on small, coiled thread
• Shot out when trigger explodes
• Used to prey on protists small animals

15
Gastrovascular Cavity

• Cnidarians have incomplete digestive tract
• No anus
• Waste, food pass through same opening

16
Polyp Body

• A tube with arms
• Stationary!
• Examples
• Hydra
• Sea Anenome
• Coral

17
Medusa

• Umbrella shape
• Mobile
• Example jellyfish

18
Jellyfish Videos

• Moon Jelly
• Note radial symmetry

• Thimble Jelly
• Interesting bell shape

19
Bilateral Symmetry

• Only 1 cut can divide animal equally
• Example
• Crawfish must be cut down middle, front to back
• Interesting body plan
• Allows head tail to differ
• Dorsal, ventral surfaces can differ
• Left and right are similar

20
The Flatworms

• Phylum Platyhelminthes
• Also have incomplete digestive tract (no anus)
• Simplest bilaterally symmetrical animals
• 3 types (Planaria, Flukes, Tapeworms)

21
The Planaria

• Two eyespots
• Have simple brain, nervous system
• Amazing healing!

22
The Flukes

• Parasitic
• Include genus Schistosoma
• Cause schistosomiasis
• Common in developing nations
• Causes anemia, abdominal pain, dysentery

23
Tapeworms

• Parasitic
• Have no digestive system!
• Very thin, can absorb nutrients directly
• Thin shape increases surface area to volume ratio
• Cause weight loss

24
7th Inning Stretch