Macroevolution Flashcards
(55 cards)
How can phylogenies be used in speciation?
shows timeline of separation of species, dividing by different events like geographical barriers forming
Cladogram
a phylogeny that only shows relationship, no absolute timing or branch length meanings
Monophyletic
group of all organisms that descend from the same common ancestor
Paraphyletic
group of organisms that descend from common ancestor, but not including all descendant groups
Polyphyletic
group of organisms with multiple independent origins
How do phylogenetic trees come about?
- using characteristics to identify organisms relationships
- homologous structures
Comparative homology
refers to the identification of structural, developmental, or molecular similarities between different species that indicate a shared ancestry
Parsimonious
the most parsimonious tree required the least number of transitions
Phylograms or molecular-branch-length trees
shows the amount of change through branch lengths
Time-scale phylogenies, dated phylogenies, time trees, chronograms
timing of branching events and timeline
What are fossils?
any trace of a past living organism, usually the harder parts of one, like bone, shell, wood, where most or the organism material has been replaced by minerals, leaving a cast
Ichnofossils
tracks, footprints, paths
Subfossils
partially fossilised remains
original biological material in the ground, may retain ancient DNA which can be extracted
Why are fossils important?
give information that may be impossible to get any other way
Different things fossils can tell us
age, morphology, biogeography, diversity, palaeocology, life history
Transitional fossils
fossils that have a collection of morphological characters that includes some, but not all, of the characters defining some taxon that humans find significant
Example of transitional fossils
Archaeopteryx
- Had feathers for flight but also teeth and a tail
- transition between a reptile and bird
Archaeopteryx: feather importance
some dinosaurs had feathers for temperature regulation
- later dinosaurs, though they didn’t fly, had feathers for courtship behaviours
Archaeopteryx: duel use
using arms for both predation (like dinosaurs) and flight (like birds)
Archaeopteryx: Feather transition
- hairlike feathers, no barbs or wind capturing surfaces, present in dinosaurs
- branching tufts of barbs
- barbs fused to a central stem, flattened
- flying feather
Archaeopteryx: Feather timeline importance
changes didnt all occur at once, many steps lead to the flying feather we see on birds today
Crown group
living group of species and their common ancestor
Stem group
any fossils that are beneath the crown group, intermediate transitional fossils
Making connections without fossils
- most organisms don’t make fossils due to small, soft bodies without hard shells or bones to fossilise
- we can use other things like DNA to understand transitions
