W1L2 - Theory of Natural Selection Flashcards
What did Darwin’s observation of the domed and saddleback tortoise?
- Saddleback tortoise survives on the more arid, southerly island. Able to crane neck up further to reach high foliage.
- Domed tortoise does not need to do that because they can reach foilage
- > Adaptation to environment
Evolution is a __ step process. Explain
- Variability
- Every individual is different with different abilities
- Variability comes from different genetic makeup
- Ordering that variability by natural selection
* Forces variability to move in a direction by natural selection
What are Darwin’s three observations
-
Fitness
- Individuals in a population, vary (e.g., different levels of memory abilities) -
Heredity
- Pass on traits (fitness) to offspring -
Competition for survival & reproduction (e.g., exams)
- Never enough resources
How are the three observations linked
Variation among individuals in population > Competition impacts on survival in given environment (fitness) > Heredity means progeny (offspring) of survivors have same traits that helped parents survive, passing on traits to their own progeny.
Superior fitness (e.g., 2x reproductive rate) can outcompete less fit variant
First step: Variability (2)
- Individuals in a population are not identical - vary
- Different size, colour, speed, camouflage, fecundity, aggressiveness, guile, strength
- e.g., Different Fish and Beatles with different characteristics
What is hereditiy (2)
- There is a mechanism of heredity whereby the offspring inherit most of the parents traits (most of their fitness from parents)
- This is the so-called Program from PICERAS
Who figured out the mechanism of heredity?
Darwin knew the mechanism, but not sure how it worked. Gregor Mendel figured out some rules of heredity by studying garden peas.
First Evidence for evolution & natural selection: Peppered moth
- White is well-camouflaged with white rocks
- Black is not well-camouflaged with rocks
After the industrial revolution, rocks were black, and the population shifted
- Variability is important because if they were no black ones, every peppered moth would be extinct
What exactly is a species
- No universal agreement
- Many go with biological species definition (individuals of same species
can breed successfully); Not applicable to organisms that don’t have sex (e.g., bacteria)
Example of biological species definition
Mule: Cross-breed of horse and dorkey
Mules are infertile/sterile, so not species (mating must be same species)
Difficulties with biological species definition: Example
Some organisms can reproduce without sex
- Banana plants are not able to breed, All grown from cuttings
- Each plant cannot be a separate species
How does speciation work? Given that the biological species definition says interbreed can’t occur. Give an example based on fruit flies (2)
- Fruit flies were fed either maltose food or starch food
- Given different fitness landscapes to survive on, found that maltose preferred to mate with one another, vice versa.
What does Fitness depend on?
Fitness depends on current conditions
Though relatively stable, if fitness landscape changes, the population genes change
What is second (strong) evidence for evolution (2)
- Fossil record is strong evidence for evolution
- Increasing complexity with passage of time
- Fossil transition series
What is Homology
- Shared ancestry (derived from common ancestral feature)
- Between humans and animals
What is the last evidence for evolution? Give examples (2)
Unity of Biochemical Processes
- All organisms share the main biochemical reactions.
- All organisms have genetic material (DNA/Program) that contains the instructions (software) on how that organism will develop
- Organisms also have proteins (hardware) to carry out the instruction
