Topic 20: Origin Of Animals Flashcards
What do ancestoral protists likely resemble?
This ancestral protist likely resembled modern
choanoflagellates, which are flagellated eukaryotes.
Choanoflagellates are _________ protists that are the closests relatives to animals
Opisthokont
Basal chaonoflagellates are ___, _____, and _____
Small, unicellular, and heterotrophic
How would you describe a chaonoflagellate?
They are collared flagellates with a funnel-shaped collar/microvilli at the base of the flagellum
What are microvilli?
re finger-like projections of the
cell membrane that captured bacteria.
What are animals hypothesized to evolve from?
Choanoflagellate-like ancestors
What are the three pieces of evidence that choanoflagellates closely resemble animals?
1) cell morphology
2) animals have a unique cell morphology
3) homolous DNA sequence
Did multicellularity evolve dependantly or independantly in many lineages?
Independantly
What are some evolutionary advantages to bein multicellular?
- the bigger you are, the harder is is to get eaten
- cell specialization
- more complexity and size
- long life span
- least predators on you
What era where multicellular animal fossils come from?
Ediacaran biota era
What are ediacaran biota?
Diverse, soft-bodied and non-motile marine organisms that have radial symmetry
Event that klet to a significat diversification of animal evolution
Cambrian explosion
What do the fossils from the cambrian explosion show
It showed a rapid evolution and increase of diversity of various bilaterian animals
(Most animals had a fossil from this era)
What are three hypothesis for the cambrian explosion
- evolution of predation: lead to more complex body structures
- oxygenation event: more oxygen suppotd greater body sizes and energtic lifestyles
- evolution of hox genes: facilitates in the diversification of complex body forms
Three eras of animal evolution
- paleozoic
- mesozoic
- cenozoic