Lecture 14 Invertebrates 1: Intro to Animals

Question 1

Ecdysozoans are

Answer 1

a group of animals, including Arthropoda, Nematoda, and several smaller phyla. The group was defined mainly based on phylogenetic reconstructions using molecular markers and includes animals that grow by ecdysis, moulting their exoskeleton.

Question 2

Hox genes are

Answer 2

subset of homeobox genes, a group of related genes that specify regions of the body along the head-tail axis of animals.

Question 3

Animal chara. (7)

Answer 3

Eukaryotic; Heterotrophic (important to cycle carbon through trophic chain); Multicellular; No cell walls; Motile at some life stage; Diploid somatic cells; Diplontic life cycle

Question 4

Chara. of animal being eukaryotic

Answer 4

• similar to fungi, ciliates, plants
• “true” nucleus
• membrane-bound organelles
• compartmentalized cytoplasm

Question 5

Chara. of animal being heterotrophic and modes of feeding (2+6)

Answer 5

• use pre-formed organic materials as energy and carbon source
• absorption takes place in a specific organ
• modes of feeding: predators, herbivores, filter feeders, parasites, detritivores, omnivore

Question 6

3 advantages of animal being multicellular

Answer 6

Having multiple cells means:
a) Cells can become specialized to carry out specific functions
b) Organisms can have longer lifespan
c) Organisms can grow in size

Question 7

What are tissues and their groups

Answer 7

Tissues = groups of similar cells organized into a functional unit
* Muscle, nervous, connective (reticular, adipose, blood, bone), epithelial.

Note: connective tissues are surrounded by non-living materials called extracellular matrix.

Question 8

Three types of structural support for animals for absence of cell wall

Answer 8

A. Hydrostatic skeleton
* ex: cnidarians, worms, shell-less mollusks*
B. Exoskeleton
* ex: shelled mollusks, arthropods*
C. Endoskeleton
* ex: sponges, echinoderms, vertebrates

Question 9

Hydrostatic skeleton

Answer 9

• Found in soft bodied organisms;
• Muscles contract – tension against fluid-filled (soft tissue) cavity
  Circular muscles increase the length
  Longitudinal muscles shorten it

Pros: efficient movements
Cons: limited capacity for limbs, restricted to wet enviroments (replenish fluids)

Question 10

Exoskeleton

Answer 10

• Firm, rigid structure for protection
• non-living covering
• does not grow with animal – molting
• “ecdysozoans” – molting animals

Question 11

Endoskeleton

Answer 11

• Rigid structure inside the body
• Internal support
• Vertebrates (living tissue)
• Some invertebrates (non-living)

ex: Spicules in sponges, Cuttlebone in cuttlefish (camouflage, buoyancy)

Question 12

Advantages of animal being motile at some life stage (3)

Answer 12

Movement reduces competition, enhances genetic diversity, expands the distribution range, etc.

Question 13

Chara. of animals having 2n somatic cells

Answer 13

Exception: male of honey bee are haploid

Question 14

Meaning of animals being diplontic

Answer 14

Diploid cycle dominates

Question 15

Animal origins (3)

Answer 15

• Life forms were unicellular for almost 3 billion years
• First animals (early sponges) evolved (700 MYA)
• Followed by the most explosive wave of diversification:
  The Cambrian Explosion (542-488 MYA)

Question 16

Describe Cambrian explosion of animals

Answer 16

• rapid diversification
• many new phyla formed
• Burgess Shale, BC
• Chengjiang, China

ex: hallucigenia

Question 17

Animals are monophyletic

Answer 17

Animals share many characteristics. Although most of their characteristics are shared with
some other groups, no other group shares all of these characteristics.

Question 18

Three lines of evidence that animals are monophyletic

Answer 18

1. Similar gene sequences
2. Similar extracellular matrix molecules
3. Unique types of junctions among cells

Question 19

Explain similar gene sequences for animals

Answer 19

Hox genes (subset of Homeobox genes):
* Genes that act in development and control the identity of different body parts along the head-tail axis;
* Evolved in a process of tandem gene duplication;
* The organization of the Hox genes in the chromosome is the same as the order of their expression –Spatial collinearity

First identified in segmented animals.

Question 20

Explain similar extracellular matrix molecules in animals

Answer 20

Matrix provides some support and communication.

Collagen fibers – the most common protein (30% of mammal proteins)
Proteoglycan complex – proteins that are heavily glycosylated.

Question 21

Explain unique types of junctions among cells

Answer 21

Tight junction, desmosome, gap junction.

May not coexist in a single cell

Question 22

Tight junctions in animal

Answer 22

seal cells together. Abundant in epithelial tissues

Question 23

Desmosomes in animal

Answer 23

connect the cytoskeleton of cells. Abundant in epithelial tissues

Question 24

Gap junctions in animal

Answer 24

act as channels between cells. Found in muscle and nerve tissues (rapid communication required)