BIOL 2390 - Topic 5 (part 1)

Natural selection

The differential survival and reproduction of individuals based on their interactions with their environment, such that some live and some don’t

Variation

Variation exists within a population, which is essential, as some traits will offer an advantage that allows individuals to survive and/or have better reproductive success

Natural selection drives ________

Evolution

Evolution

The change in gene frequencies, driven by differences in fitness (i.e. survival and reproduction), such that the favourable traits will increase in frequency over time, while the unfavourable ones decrease

Natural selection vs. evolution unit

Natural selection acts on individuals, but evolution acts on populations

Natural selection on camouflaged groupers

Groupers with darker coloured bodies are selected for, such that they are more likely to pass on their genes and make up a majority of the population in the next generation, while those with light coloured bodies are selected against

Adaptations

A heritable trait, either behavioural, morphological, or physiological that is shaped by natural selection over time

Effect of adaptations

1.) It enhances overall growth, survival, and reproduction

2.) It can also affect interactions within and between species, such that it can form positive relationships between them

Adaptations in different conditions

1.) Adaptations are optimized for specific environmental conditions, meaning they will not work when put into other conditions

2.) In fact, they are likely to act as hindrances instead

Phenotypes vs. genotype

Genotypes are an organism’s genetic makeup, which determines the observable traits, i.e. the phenotype, that they possess

Simple dominance

Phenotypic variation is limited, usually only dominant and recessive, making it easy to interpret

Are all traits easily observable?

No, such as body biochemistry

Complex phenotypes

More complex phenotypes can be observed in codominant and continuous distributions

Codominant phenotypes

When the heterozygous genotype results in a blended product

Are codominant and continuous phenotypes bad?

No, they generally just increase phenotypic variation

Continuous phenotypic traits

Refers to when more than one set of genes are responsible for a particular trait, such as height, skin colour, blood pressure, etc

Advantages of continuous traits

It leads to greater genetic and phenotypic diversity

Influence on continuous traits

1.) They are not only determined by genetics, but also by environmental factors

2.) For example, your genes can dictate your optimal height, but not receiving the proper nutrients growing up can prevent you from reaching your full potential height

Phenotypic plasticity

1.) Refers to organisms that can change their phenotype based on environmental conditions

2.) They have a set genotype, but the flexibility is encoded in their genome

Degree of plasticity

It varies among species, some have a lot, some have very little

Phenotypic plasticity example

Salmon, who can change their morphological appearance when they go from the ocean back into the freshwater lake they were born in

Advantage of plasticity

It increases fitness, as it allows organisms to survive and utilize multiple different environmental conditions