Adaptation and natural selection 2 Flashcards
Each adaptive trait represents a trade-off with _____ ___ ______
Each ADAPTIVE TRAIT represents a trade-off with COSTS AND BENEFITS
can selection cause substantial changes within a population?
- yes, a good example of this is artificial selection (through human intervention)
- we have created many diverse domesticated plants, foods, and animals (such as dogs) through artificial selection and selective breeding)
Who was darwin influence by?
- Thomas Malthus and his concept of population growth
- basically populations increase faster than food supplies, which creates pressure and selection
What is natural selection?
- process where organisms with the best adaptations for their environment survive, reproduce, and pass their genes to the next generation
Natural selection is a 4-step process:
- overpopulation
- competition (struggle for existence)
- variation in success
- inheritance of traits
How does overpopulation contribute to natural selection?
- there are more organisms born than the environment can support
- not enough resources for all individuals
How does competition contribute to natural selection?
- organisms compete with other members of the population for resources (food, shelter, water, mates)
How does variation in success contribute to natural selection?
- organisms in a population are not all the same, there is variation in phenotypes and differences in fitness
- those with better adaptations are more successful than organisms without these adaptations so they tend to live longer and reproduce more
- (if all individuals were identical, there would be no chance for differential survival/success)
How does inheritance of traits contribute to natural selection?
- genes that cause adaptations are passed from one generation to the next, changing the gene pool and causing changes in the overall traits of the species
- beneficial adaptations appear more frequently
Selection only acts upon ______
PHENOTYPE
What is the mechanism through which evolution occurs?
Phenotypes
Natural selection arises when…
- individuals vary in expression of their phenotype
- this variation causes some individuals to perform better than others
What is the best way to measure fitness?
- lifetime reproductive contribution, and how many offspring survive to reproduce
- COMBINED fitness
How does reproductive success have fitness trade-offs with ability to survive? How are these conflicting selection pressures
- sometimes features that increase a species reproductive success (things that females find attractive) will have consequences with predation (makes it harder for them to escape or easier to see)
Natural selection only works on ________traits
Natural selection only works on HERITABLE traits
while other mechanisms for evolution are random, ________ _______ is NOT random
NATURAL SELECTION
what 3 elements are KEY to creating natural selection
- variation
- differential reproduction
- heredity
it is important to note that ____ _____ does not create PERFECTION or GUIDES evolution, it simply is a process
NATURAL SELECTION
