W1 Evolution, Tree Thinking, Human Story Flashcards
What is a Phylogeny?
Phylogeny is the study of relationships among different groups of organisms and their evolutionary development.
What is Homology vs Homoplasy?
Homology, is the development of different species of organisms based upon their descent from a common evolutionary ancestor. (Descent)
Homoplasy is shared characteristics between two or more animals that did not arise from a common ancestor. (Convergence)
Define biological evolution
Biological evolution is the change in inherited traits over successive generations in populations of organisms.
What is the difference between a proximate and an ultimate
explanation for behaviour?
Give examples.
Proximate causes are the mechanisms directly underlying the behaviour. i.e. The underlying hormonal response, which is triggered by separation from the herd.
In contrast, the ultimate causes of social behaviours include their evolutionary or historical origins and the selective processes that have shaped their past and current functions.
i.e. The development of a better defense against predators that results in increased survival of individuals remaining in groups would be an ultimate cause for the tendency to reunite with the herd.
So what is an allele?
Different possible
forms of a gene
What is Micro-evolution?
Any change in the frequency of alleles within a
gene pool from one generation to the next.
What is Genetic drift?
Chance event causes a change in the frequency of
alleles in a population
What is the founder effect?
It is a bottleneck that occurs when a
small group colonizes a new location. A form of genetic drift.
What is Gene flow?
If a barrier exists between two populations then complete interbreeding is not
possible.
Allele frequencies in each population will vary independently.
Then if a species is mobile in some way: flight, walking, pollen etc. individuals can
enter isolated populations and change the frequency of alleles
What is Mutation?
The introduction of variant alleles to a
population via a change in the genetic
material of the reproductive cells.
What is selection?
How is a trait naturally selected for?
When an organism reproduces due to a specific trait.
If trait affects the probability of
an organism passing on its genes to the next
generation, it’ll appear more
What is Natural Selection?
Natural selection occurs when heritable
differences in organisms lead to differences in
their reproductive output
What is Artificial Selection?
When people choose
What is Sexual Selection?
Sexual selection occurs when species choose their mates, and may choose based on traits that don’t necessarily infer fitness.
Does selection act on species as a whole?
Individuals, not species.
Natural selection acts on individuals, not a whole
species: individuals reproduce or die.
Natural selection not ‘for the good of the species’
What are Spandrels?
Features that may look like adaptations but in fact are simply byproducts of design constraints (spandrels).
What are Exaptations
Features that may once have been a byproduct or were adaptive for one function may have changed over time to serve a different function - exaptations (e.g. feathers).
What does “Trees not ladders” mean?
That evolution is not hierarchical, but simply branches.
What is Phylogenetics?
(Greek: phyle = tribe, race and genetikos =
relative to birth, from genesis = birth) is the
study of evolutionary relatedness among
various groups of organisms (e.g., species,
populations).
How do you read a phylogenetic tree?
Trees show the evolutionary relationships between the species at the tips.
We read a tree as a set of hierarchically nested groups, which we call
clades. DON’T JUST FOCUS ON THE TIPS!
What are the parts of the tree?
Root (common ancestor), the root of the tree.
Node, where a species deviates.
Clade, a group of related taxa.
Tip or ”leaf”, a species.
What does phylogenetics teach us?
The relationship between all organisms.
When organisms split from one another.
There is no scala naturae (ladder).
How character states have evolved.
What are the milestones of Human Evolution?
1: Walking upright (“Lucy” (3.2Mya) Australopithecus)
2: Stone tool manufacture(2.5 Mya )
3: Fire (690-790 Kya)
4: Big game cooperative
hunting (400Kya ) (Spears)
Hafting (200Kya)
5: Symbolic culture (93-110Kya)
Ritual burial, jewellery, cave paintings . Music (400Kya)
What happened to the Hominin brain size?
Neocortex expansion.
The high, straight forehead that characterizes modern humans, superceding the
prominent brow ridges of others hominids, is due to the expansion of the cortex,
and especially the prefrontal cortex, in our species.
