Ecology Lesson 6 Flashcards
Behavioural ecology
Why particular kinds of behaviours persist in animal populations even if they seem counterintuitive/ will eliminate others.
Behaviour and natural selection
Those with more appropriate behavior pass on more genes (in context of the environment):
* More likely to survive
* More likely to produce offspring
Passing on genes makes it become fixed.
How can genes disappear?
If an individual dies before it gets the chance to reproduce.
Individual fitness with benefit and costs
- Benefit: if fitness increases
- Cost: if fitness decreases
Fitness
Refers to evolutionary fitness. How likely an individual is to pass on its genes.
Actor
the animal performing the behaviour
Recipient
is or are the other animals involved
Cooperative
+ for both actor and recipient.
ie. defense and hunting for living in a pack.
Selfish
Actor is + and recipient is -.
ie. territoriality, as the actor gets the resources but the recipient gets none of the resources.
Spiteful
- for both actor and recipient.
ie. killing more food than you can eat.
Altruism
- for actor and + for recipient.
ie. alarm calls in pikas
Pika
Live in the rocky areas in North America. They live in groups. One will have do an alarm call to warn others of predators (like weasels) to tell others to go and hide, but this increases risk to self. There relatedness is high, so it’s worth it to do it.
Inclusive fitness
There is more going on in terms of passing in genetic material.
Total effect on number of genes passed on:
1. Producing offspring
2. Aid relatives to produce more offspring (as you share some genetics with your relatives) so it increases the number of copies of some of your genes in the gene pool.
Kin selection
Selection for an act that enhances a relative’s reproductive success. Some genetic material is shared with relatives (i.e. have some of the same genes).
Genes are passed on not just through offspring
but also through relative’s offspring.
Hamilton’s Rule
Natural selection (evolution) favours an act
if C< r*B
* C: Cost to altruist (lost reproduction)
* r: Relatedness (fraction of genes shared)
* B: Benefit to recipient (increased reproduction)
Relatedness (r)
The child gets one set of alleles form each parent. Parent and child share half their alleles. Therefore, their relatedness is ½ (0.5).
Relatedness equation for successive generations?
r=(1/2)^n
n= number of links
Relatedness between grandmother and granddaughter?
It’s 0.25
Relatedness of siblings?
r=0.5
Does it increase (evolutionary) fitness to save
a sibling if you die in process?
c=2 r=0.5 b=2
2 is not less than 1
Answer: No
Does it increase (evolutionary) fitness to save
a sibling if you may die in process?
C = Risk of dying x lost reproduction. Assume a risk of dying of 20% (0.2). C = 0.2 x 2 children (average)
C = 0.4, r=0.5, b=2
0.4<1
Answer: Yes
What does C depend on?
The risk of dying and the risk that you don’t succeed in saving the other people.
Reciprocal altruism between non-relatives
- Tit for tat. Chimps may groom another chimp hoping it will do the same for the them in the future.
- Stable social groups for it to work.
A part of social cohesion that keeps animals living together in groups.
Social Organization (benefits and costs)
Being social – when is it worth it to live in a group?
Benefits
* Cooperative feeding
* Defense of group (safer)
Costs
* Disease/parasites (higher chance of getting one)
* Restricted reproduction (can’t pass on genes)
Group living evolves when benefits > costs
