Chapter 17 Natural Selection, Factors affecting natural selection and hardy Weinberg principles
17.3 - Natural Selection
1. Selection pressures and how they influence organisms
2. The steps involved in natural selection
Selection pressures
All organisms encounter selection pressures, which are environmental factors that affect their
survival and reproduction. The organisms that are best adapted to these selection pressures have a
higher chance of passing on their traits to future generations.
Selection pressures include:
Predation
Competition for resources
Climate change
Disease
Fitness describes an organism's ability to survive and reproduce. Those with higher fitness are more
likely to transfer their genes to the next generation.
How natural selection works
An allele is a variant form of a gene. Different alleles can result in different observable traits.
Genetic diversity is the total number of different alleles in a population. This leads to variation as
different combinations of alleles mean different proteins are produced, resulting in different
characteristics.
Genetic diversity influences natural selection as organisms with advantageous traits are more likely
to survive, reproduce, and pass on their alleles, influencing the gene pool. The more successful an
organism is at reproducing, the more likely its alleles will be passed on to the next generation,
increasing the allele frequency.
The process of natural selection includes these key steps:
1. There is variation in characteristics within a species.
2. More genetic variation emerges within a population due to random mutations.
3. Individuals with alleles that code for traits that are advantageous for survival are more likely
to reproduce.
, 4. These advantageous alleles are passed down to offspring.
5. Over time, these beneficial alleles become more common in the population.
This mechanism leads to populations becoming more adapted to their environment over
generations.
17.3 - Natural Selection
1. Selection pressures and how they influence organisms
2. The steps involved in natural selection
Selection pressures
All organisms encounter selection pressures, which are environmental factors that affect their
survival and reproduction. The organisms that are best adapted to these selection pressures have a
higher chance of passing on their traits to future generations.
Selection pressures include:
Predation
Competition for resources
Climate change
Disease
Fitness describes an organism's ability to survive and reproduce. Those with higher fitness are more
likely to transfer their genes to the next generation.
How natural selection works
An allele is a variant form of a gene. Different alleles can result in different observable traits.
Genetic diversity is the total number of different alleles in a population. This leads to variation as
different combinations of alleles mean different proteins are produced, resulting in different
characteristics.
Genetic diversity influences natural selection as organisms with advantageous traits are more likely
to survive, reproduce, and pass on their alleles, influencing the gene pool. The more successful an
organism is at reproducing, the more likely its alleles will be passed on to the next generation,
increasing the allele frequency.
The process of natural selection includes these key steps:
1. There is variation in characteristics within a species.
2. More genetic variation emerges within a population due to random mutations.
3. Individuals with alleles that code for traits that are advantageous for survival are more likely
to reproduce.
, 4. These advantageous alleles are passed down to offspring.
5. Over time, these beneficial alleles become more common in the population.
This mechanism leads to populations becoming more adapted to their environment over
generations.
