Adaption & speciation (Lucy) Flashcards
Are adaption & speciation the same thing?
Not necessarily
Adaption can happen in species whereas speciation is how new species arise
How can adaptions happen within a species?
There can be variation within a species for a trait (such as colour, flowering time & growth rate)
Give an example of an experiment on adaptions:
Climatic selesction on shell colour in Capaea nemoralis (type of snail)
How was the experiment on Capaea nemoralis conducted?
Denim was stuck to the shells of the snails
The rate of fading tells the researcher whether the snail has been more in shade or sun
Snails were either yellow or brown & they all had different amts of bands on them
What were the results of the experiment on Capaea nemoralis shell colour?
Found that the lighter in colour (yellow morphs) snails spent more time in the sun
& also the snails with fewer bands spent more time in the sun
Denim was most faded on these
Give 2 examples of adaptions occurring quickly:
- Antibiotic resistance in bacteria
- Pesticide resistance in insects (this is slower than bacteria tho)
How can antibiotic resistance occur quickly in bacteria?
New mutations arise & are selected for the population
This happens so quickly bc they spread rapidly on plasmids
How can pesticide resistance occur quickly in insects?
Selection for resistant types already in the pop at very low freq –> ‘standing genetic variation’
If a pesticide is applied to a pop, it will wipe out the non-resistant individuals, the survivors (resistant) will reproduce & form the next generation of resistant individuals
What happens to the amount of resistant speciesif more pesticides are added to plants?
The numebr of resistant species will increase
Give an example of an insect that is resistant to pesticides:
The Colorado potato beetle, Leptinotarsa decemlineata
Resistant to a wide range of insectecides
If pesticides are removed from plants what happens to the number of resistant insects & why?
Remove the pesticide = no. resistant insects decreases
This is bc if resistance is costly then there will be selection favouring the non-resistant types IF pesticide treatment is removed
What 2 factors can affect the relative “fitness” of different variants in species?
- The abiotic environment (e.g. temperature, presence of pesticide)
- The biotic environment (e.g. presence of other species, abundance of own species eg frequency dependence)
What are conspicuous polymorphisms thought to be influenced by?
Give an example
External factors such as preadtors
e.g. Predation of Cepaea (snails) by birds
How does birds predation of Capaea influence influence the snails polymorphisms?
Birds have an innate preference for brown but also learns which morph is most common & preferentially predates on that
Predators are known to favour common morphs in many cases = rare morphs having an advantage
Brown snail no. will decrease & become rare
Pink & yellow more popular so the preference of birds shift to the popular one
This happens in a cycle
How is the polymorphism in the Hawaiin spider maintained?
Thru frequency dependent selection
What happens as a morph becomes less rare?
It loses its advatage & a stable equilibrium can result
What is negative frequency dependent selection?
Fitness DECREASES as a morphs becomes more common
It keeps variation in the population
(This was alos written on this slide but not sure how to put it onto a fc = Not just predation - variation in Major Histocompatibility Complex thought to be maintained by host-pathogen co-evolution)
What is an example of balancing selection?
Negative frequency dependent selection (Positive is also an example)
What is negatvie freuqency dependent selection proposed to explain?
Persistence of colour morphs in some spiders and snails for example
What is postive frequency dependent selection?
Fitness of a morph INCREASES as it becomes more common - would eliminate the rare morph
e.g. rare morph so rare it can’t find a mate
Remove variation from the population
Give an example of how positive frequency dependent selection removes variation from the population?
Warning colouration to advertise unpalatableness & thus deter predators
When a morph is common, it’s more likely that birds will have already learned to avoid it
When a morph is rare, birds will not yet have learned to avoid it. An individual of a rare morph is therefore more likely to get eaten (i.e. gets killed while educating the bird)
The fitness of each morph is positively frequencey dependent
Are benficial adaptions always more frequency?
No
There may be thresholds in terms of actual number rather than freq –> so 1 individual with the trait in question is needed per group regardless of grp size
e.g. colour vision in New World primated
Give an example of frequencey in a New World priamte with colour vision:
New World Monkey species
Males in most New World Monkey species are always dichromatic
Females are EITHER dichromatic (see blues & greens) or trichromatic (see blues, reds & greens) –> depends on the number of different opsin alleles they carry on their X chromosome
How is the opsin carried in male and female monkeys?
- S opsin, carried by males & females on chromosome 7
- M and L are 2 opsin alleles at the same locus on the X chromosome (males have one, female two)
(Female can have 3 alleles)
