Invertebrates Lecture 1: Introduction to Animals

Question 1

What are the seven characteristics of animals?

Answer 1

1. Eukaryotic
2. Heterotrophic
3. Multicellularity
4. No cell wall
5. Motile at some life stage
6. Somatic (body) cells are diploid
7. Diplontic

Question 2

What does it mean to be eukaryotic?

Answer 2

Animals are multicellular organisms with a nucleus and complex organelles.

Question 3

What does it mean to be heterotrophic?

Answer 3

Animals use pre-formed materials as energy.

Question 4

What does it mean to have multicellularity?

Answer 4

This means that organisms live longer and grow and they can carry out specific functions.

Question 5

What does it mean if animal cells do not have a cell wall?

Answer 5

It means that they have different ways to sustain shape:
1. Hydrostatic skeleton - muscles contract against fluid filled cavity (worms)
2. Exoskeleton - external molting (dragon fly)
3. Endoskeleton - internal structure (humans)

Question 6

What does it mean to be diplontic?

Answer 6

Having a diploid dominant life (2n).

Question 7

What are the animal origins?

Answer 7

1. Animals are monophyletic
2. first animals (early sponges) evolved (700 MYA), then the cambrian explosion followed (542-488 MYA)
   
   • the most explosive wave of diversification

Question 8

Why are animals deemed monophyletic?

Answer 8

1. Similar gene sequences (Hox genes: control the identity of different body parts)
2. Similar extracellular matrix molecules
3. Unique types of junctions among cells

Question 9

What are the three types of junctions among cells?

Answer 9

1. Tight junctions: seal cells together
2. Desmosomes: connect the cytoskeleton of cells
3. Gap junctions: act as channels between cells