Phylogeny, Animal Evolution & Divergence Flashcards
(16 cards)
What were the first animals?
Ediacara biota (stationary, plant-like organsisms that fed on microorganisms in nutrient rich shallow oceans)
–> often bilateral
What was the first evidence of animals?
Biomarkers (Mass Spec)
–> animals exclusively produce cholestorol, cholestane (derivative) found in rock strata that predate fossilised Ediacara biota
3 Shared characteristics of animals
1) Heterotrophy (attaining energy from consuming other organisms)
2) Multicellular (composed of multiple cells)
3) Motility (mobile/can move at some stage of their life)
Early evidence of predation
550MYO fossil bore hole through shell (ev of being attacked)
What happened during Cambrian Explosion?
large increase in diversity of life on earth, (variety in size, diet, survival strategy)
(due to increased O2, nutrients - organic matter)
Linnaean Taxonomy?
Carl Linnaeus
1) Binomial Nomeculture: Genus species (G. species)
2) Hierarchial Classification:
domain>kingdom>phylum>class>order…
3) Phylogenic classification
classified by their relationship to ancestral species
Cladogram (branching type)
purely shows relationships, distance of branches do not show timescale.
Phylogram (branching type)
branch length= est. amount of evolutionary/genetic change
branches don’t end in same place
Chronogram (branching type)
branch length represents time.
Why is was the process of making phylogenic tree flawed?
Placed similar species closer together by anatomical similarities (bones, features, behaviours)
–> convergent evolution could result in unrelated species evolving to resemble one another as a result of similar selection pressures.
How is phylogeny defined now via genetic relatedness?
amount of genetic difference determines closeness on tree.
amount of mutations in genomes, allow us to know how related two species are and when they diverged.
How do you determine genetic relatedness using phylogeny?
By comparing and contrasting the amount/number of mutations in the genome and where they are.
2 Types of homologous genes (2 diff species, common ancestor gene)
Orthologous genes : same ancestor gene (same mutation)
Paralogous genes : genes that duplicated at some point from single ancestral gene
How are molecular clock and genetic divergence related (eq)
Number of mutations is linearly related to the amount of time since lineages diverged.
What are the characteristics of the “Bilateria” clade?
1) Bilateral symmetry
2) Cephalisation (development of head)
3) One-way digestive system
4) Embryo made of 3 germ layers
Deuterostomia vs Protostomia
Within bilatera clades (defined by events in development)
Proto - mouth forms first
Deutero - anus forms first (vertebrates)
