pressures that cause a change in the allelic frequency. Stronger cause greater change, Such things are climate change, pesticides, predation, and antibiotic resistance.
What is needed for natural selection to occur?
1) variability in traits within a population
2) variation is a heritable trait
3) substantial mortality within the population; some need to die and some need to live
4) most favorable traits are better at surviving and reproducing
How does predation strength (selection pressure) effect traits (how do they become better adapted to the situation)?
- type of moth can be light or dark colored over in england. Before the IR most of the moths were lighter colored and blended in with the lichen on the trees. However after the IR the trees were covered in soot, so the light colored were eaten by birds and the dark colored moths became prominent.
there will always be some of the less dominant to keep variation in case the conditions change again, otherwise the population would die out
Soapberry Bug example
originally this bug had a short mouth due to the food source it had (flat-podden golden rain tree fruit) but due to the introduction of a non-native plant food called the Balloon fruit, which was much larger, the bugs with longer mouths survive and the population become dominated by these long mouth soapberry bugs.
Contemporary example of adaption (natural selection)?
Darwins finches; their environment periodically goes through wet and dry season. During the dry season they have smaller beaks which are better for smaller nuts. During the wet season they have larger beaks which are better for the larger nuts.
Other examples of NS (adaptation)
- pesticide resistance in insects
- antibiotic resistance in bacteria
- herbicide resistance in weeds
- HIV resistance to anti-retroactive drugs
What is the fix for the issue of insects, bacteria, weeds, HIV adapting to our means of killing them?
switch between methods
or use less often
Are the processes of adaptation random?
- NS (no)
- migration (yes) dispersal from another population (think finches over ocean)
- genetic drift (yes) usually occurs by founders effect or bottleneck
How is plant and animal breeding like natural selection? How is different?
- results in a change in genes
- however selection is different; we decide in artificial selection and in NS nature chooses
- we choose cute traits, nature chooses traits for survival and reproduction
What is founders effect?
when a few individuals from a population start a new population and it has a different allele frequency from the original population
- generally less variation and more susceptible to having rare genes and illness
ex. amish or moose/wolf population on Isle Royal
What is genetic drift?
random change in allele frequencies
ex. cheetahs or northern elephant seals
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