Evolution Flashcards
What did Dobzhansky say?
“Nothing in biology makes sense except in the light of evolution”
How can complex adaptations evolve?
They can have intermediate forms which are also advantageous.
Simple eyes are useful for light detection.
Wings are useful for gliding.
What are limits to adaptation?
Crossing maladaptive valleys.
What is fitness?
Mathematical measure of differential transmission.
What is convergent evolution?
Evolution of similar traits due to the need to adapt to similar environments.
Example of convergent evolution?
Echolocation:
As a sensory adaptation, echolocation evolved separately in dolphins & whales, and bats. From the same genetic mutation.
Eyes:
Camera eye of cephalopods, vertebrates and cnidaria. Their last common ancestor had a simple photoreceptive spot.
Cephalopods don’t have a blind spot as blood and nerve vessels enter from the back of the retina.
What is micro-evolution?
Change in allele frequencies that occur over time within a population. Occurs over a relatively short period of time.
What is macro-evolution?
Evolution on a scale at or above the level of species.
Major evolutionary change, especially with regard to the evolution of whole taxonomic groups over long periods of time.
What is Hamilton’s rule of relatedness?
When r b - c > 0 genes should increase in frequency.
R - coefficient of relatedness
C - costs in fitness
B - benefits in fitness
Explains altruism towards family. Kin selection occurs as family members also carry your genes, so by aiding their survival your genes have more chance of being passed on.
When can altruism occur without relatives?
When reciprocal altruism occurs, as there will be a later benefit.
Example of kin selection?
This can be seen in eusociality, where there is cooperative brood care and specialised castes of non-reproductive individuals.
Social insects provide a good example of kin selected traits, as the workers of some species are sterile. This wouldn’t occur if individual selection was the only process occurring.
In a colony of Hymenoptera, the relatedness coefficient is unusually high due to haplodiploidy, meaning that the benefits in fitness for the workers exceed the costs of lost reproductive opportunity, and there are large groups of non-reproductive individuals.
Example of reciprocal altruism?
Vampire bats also display reciprocal altruism, as described by Wilkinson. The bats feed each other by regurgitating blood. Since bats only feed on blood and will die after just 70 hours of not eating, this food sharing is a great benefit to the receiver and a great cost to the giver.
To qualify for reciprocal altruism, the benefit to the receiver would have to be larger than the cost to the donor. This seems to hold as these bats usually die if they do not find a blood meal two nights in a row.
Example of allopatric speciation?
The Isthmus of Panama only arose some 3 million years ago.
Snapping shrimp.
Shrimp on one side of the isthmus appeared almost identical to those on the other side – having once been members of the same population.
But when she put males and females from different sides of the isthmus together, they snapped aggressively instead of courting. They had become separate species, just as the theory would predict.
What is lekking?
Competition for mates between males?
What is intrasexual selection?
Selection occurs within one sex, generally males fighting each other to find a winner.
Results in sexual dimorphism.
