The evolution of animals Flashcards
What are the features of animals?
- multicellular
- heterotrophic
- no cell walls
- often mobile
Of all the single-celled organisms known to exist, which organism is the most closely related to multicellular organisms?
Choanoflagellates
When are geological time scales used?
Used to show when major events occurred and the effects this had on life on earth
Why might a fossil record be incomplete?
Because many soft bodied organisms do not fossilize easily.
- can be consumed by other animals
- not every part can be preserved
Why did arthropods develop an exoskeleton?
for protection, structural support and thrived
Which characteristics gave the arthropods advantages ?
Jointed appendages allowed arthropods to have much greater flexibility and range of movement. Advantages of having a hard outer layer are protection, water retention, structural support (particularly on land), and counterforce for attachment and contraction of muscles
What advantages does an external shell give over an exoskeleton?
external shell: doesn’t need to be used to movement so much thicker and more protection
exoskeleton: less thicker, but able to move and flexible, but still protection
What advantages does having a jaw provide?
- ability to use new resources
- chewing
- biting
- adaptive immune system evolved in jawed vertebrates due to the evolution of jaws
Two major groups of fish:
Cartilaginous fish and bony fish
What are the two major groups of the bony fish?
- the lobe-finned fish with bones in their fleshy fins
2. The ray-finned fish
What did the lobe-finned fish give rise to?
- amphibians
- reptiles
- birds
- mammals
What did the ray-finned fish give rise to?
most fish species living today
What did tetrapods have?
they had primitive lungs and lobed fins/limbs
Name 6 adaptations to terrestrial life.
- temperature changes
- air breathing
- structural support
- dehydration
- reproduction
- UV radiation
What do amphibians have?
- moist skin
- simple lungs
- non-amniotic eggs that have to be kept moist
Why do amphibians require less food?
Because they are cold-blooded
What does a layer of keratin do for reptiles?
A layer of keratin forms scales to waterproof
the skin
What does the eggs of reptiles have?
- amniotic membrane and soft shell
What are sautopsids?
Include all the modern reptiles, plus the dinosaurs and birds
What are the features of dinosaurs?
- laid shelled eggs
- some cared for their young
- warm-blooded altho reptiles
- may have required a high metabolism to support size and level of activity
- blood flow through bones, bone growth patterns support warm-blood
- lived on land
What were the dinosaurs that lived in water?
Ichthyosaurs
Two groups of dinosaurs:
lizard-hipped and bird-hipped
What happened when a meteorite hit earth?
It caused volcanic activity and climate change. the earth was dry and hot and large organisms didn’t have enough food to survive, so small organisms survived.
What are the features of birds?
Feathers Hollow bones Elongated metacarpals Wishbone Sternal keel Air sacs as well as lungs Only one of some organs to save weight Hard shelled eggs Beak made from keratin
