Lecture 17

Question 1

Characteristics of all animals and most animals

Answer 1

All : Eukaryotic, no cell wall
Multicellular, Heterotrophic

Almost All: Tissues, organs, organ systems
In all animals except sponges: they don’t have any tissues

Nervous & muscle & tissue: this is unique to animals
All animals except sponges
Almost all (fyi ~97%) animals are invertebrates.

Most: motile, reproduce sexually, bilateral symmetry

Question 2

challenges to living on land & the adaptations

Answer 2

Water loss = Can dry out (desiccation)
(waxy cuticle in invertebrates, tough skin in vertebrates)

Gas exchange = Reduced due to waxy cuticle. (lungs, tracheal tubes) NB wrt O2: more on land than in water

Structural support= Gravity may cause collapsing (skeletal system)

Reproduction = Internal fertilization (except for amphibians)

Question 3

Classification. Be able to name one animal from each of the 9 phyla presented.
Know that most (fyi 75%) of animals are in a single phylum (fyi Arthropoda), which have exoskeletons & are invertebrates

Answer 3

Chordates

Birds, fish, reptiles, mammals

Question 4

Cambrian explosion

Answer 4

Cambrian Age: geological period b/w ~540-490 million years ago.

“Cambrian explosion: abrupt appearance of major animal groups: lasted ~ 10 million years (fyi ~540-530 mya)

Based on fossil records: only 2 phyla present before the Cambrian explosion (fyi porifera ie sponges & Cnidaria ex jellyfish) ie only water-dwelling animals

Some paleontologists estimate that as many as a 100 phylum were created over the period of only tens of millions of years

Question 5

3 Skeletons

Answer 5

Exoskeleton: external, surface (since this is the type of skeleton in invertebrates, it is the most common type of skeleton)
Support, protection

Endoskeleton: internal (in vertebrates)
Support, protection of internal organs, movement, store minerals

Hydrostatic skeletons: fluid under pressure in a closed body compartment
movement

Question 6

Sexual reproduction in vertebrates

Answer 6

Sexual reproduction much more common

MOST aquatic organisms lay eggs → external fertilization

Most fish (cold-blooded) - External fertilization 
Sharks have internal fertilization 

Amphibians (cold-blooded) - External fertilization

Internal Fertilization
& have amniotic egg

Reptiles (cold-blooded)internal fertilization

Birds (warm-blooded)internal fertilization

Mammals (warm-blooded)internal fertilization

Question 7

Amniotes Internal fertilization

and Ammonitic egg

Answer 7

Internal fertilization: prevents desiccation of sperm & egg

No longer necessary to return to water to reproduce
Compare this with vascular seed plants

Amniotes: vertebrates which have a fetal tissue known as the amnion, which surrounds and protects the fetus
Reptiles, birds, mammals

Amniotic cavity with fluid: protects from injury & dehydration (no desiccation of developing offspring)
Yolk sac: nutrients