Introduction Flashcards
What percentage of all animals on Earth vertebrates?
4%
What is the main way to divide the vertebrates? Explain them
Amniotes and non-amniotes
Non-amniotes = embryos are enclosed by membranes from the female reproductive system (fish and amphibians)
Amniotes = have additional membranes from the embryo aka amniotic egg (reptiles, birds, mammals)
How can the amniotes be split?
Sauropsids = reptiles and birds
Synapsids = mammals
These divereged over 300 MYA but show some convergent evolution e.g. endothermy
What are the tetrapods?
Animals with four limbs and includes amphibians and the amniotes - they evolved from the fish
What are the two types of classification methods?
Phylogenetic classification = weights characters depending on evolutionary origin - uses morphological and molecular studies
Phenetic methods = equal weight is given to all charcters - only look at morphology and so this can cause misunderstandings with convergent evolution
Give an example of homology
Forelimb in vertebrates
Describe the forelimb of a vertebrate
Have a humerus
The radius (lateral) and ulnar (medial) attach to the humerus
These end in the carpals
Carpals attach to the metacarpals
Metacarpals end in the phalanges - most vertebrates have 5 (pentdactyle limb) but some have lost digits e.g. horses only have digit 2 and 4
Give some examples of convergent evolution
Cichlids in African Great Lakes - cichlids evolved separately in different lakes but have similar morphologies and functions
The fusiform body shape found in sharks, porpoise and the ichthyosaur
How many orders are found in the tetrapods? What can this indicate
Mammals - 27
Birds - 41
Reptiles - 4
Amphibians - 3
Orders can indicate diversification in particular groups rather than using the number of species
Give a simplistic overview of how the Earth has changed over time
550 MYA there were separate continents
300 MYA the continents formed one single continent (due to continental drift) known as Pangaea - this is the main birthplace of terrestrial vertebrates
150 MYA Pangaea broke apart - this fragmentation allowed birds and mammals to start to diversify
What is the deepest found vertebrate?
Snail fish - found in the Mariana Trench
What fish has the fatest growth rate?
Killfish - goes from eggs to a reproductive stage in 17 days
When did vertebrates reach their maximum?
12-14 MYA
For each living species, could be as many as 100 extinct species
Give some examples of extinct or threatened vertebrates. Why are they extinct/vulnerable?
Thylacine - extinct due to hunting from farmers
Golden toad and Southern gastric brooding frog - extinct due to chytrid fungus
Cave fish - endangered due to people extracting water from the caves they live in
20% of vertebrates are endangered
