Genetic diversity, natural selection and adaptations

What is an allele?

An allele is a variant form of a gene. Different alleles can result in different observable traits

What is genetic diversity?

the total number of alleles or genes in a species or population

How does genetic diversity influence natural selection?

Genetic diversity allows organisms with advantageous traits to survive, reproduce, and pass on their alleles, influencing the gene pool.

What happens to allele frequency when advantageous traits are passed on?

The allele frequency increases in the population as successful organisms will be more likely to reproduce

What does the acronym IVESRAS stand for in the context of natural selection?

Isolation, Variation (due to random mutation), Environmental adaptation, Survival, Reproduction, Allele frequency, Speciation.

Explain the process of natural selection, ensure to include all of IVESRAS

Isolation of the species

Due to random mutations or different alleles being introduced into the population when individuals from another population migrate into them and reproduce (known as gene flow) there will be variation in characteristics

Therefore if these variation in these characteristics allow the species to be more suited for environmental conditions, then they are more likely to survive so at this point there is a change in allele frequency since there is a higher proportion of the advantageous alleles then the previous alleles

Therefore individuals with alleles that code for traits that are advantageous for survival are more likely to reproduce

So these advantageous alleles that are better suited to the conditions are passed down to offspring

Overtime these beneficial alleles become more common in the population and eventually speciation may occur (a new species is produced)

This new species and the original can now longer interbreed

What is gene flow?

Gene flow is the introduction of different alleles into a population when individuals from another population migrate and reproduce.

What are adaptations?

Adaptations are inherited characteristics that enhance an organism's ability to survive and reproduce in its specific environment.

What are the three categories of adaptations?

Anatomical, Behavioral, and Physiological adaptations.

What is anatomical adaptations?

Physical structure, both internal and external

What is an example of anatomical adaptation?

Mimicry, teeth, body coverings such as fur and feathers.

What is a behavioral adaptation?

A way an organism acts that increases its chance of survival and reproduction

Examples of behavioural adapatations?

Defensive responses such as freezing to avoid detection by predators, courtship display such as dancing to attract mates, seasonal actions such as migration of birds

What is a physiological adaptation?

Internal biological systems and functions

Examples of physiological adaptations

Venom, storage of water, and lowering rate of metabolism during hibernation

What is directional selection?

Directional selection occurs when individuals with alleles for extreme characteristics are more likely to survive and reproduce, often in response to environmental changes.

Give an example of directional selection.

The development of antibiotic resistance in bacteria.

Explain the process of directional selection in the development of anibiotic resistant bacteria

At first, none of the bacteria are resistant to an antibiotic but randomly one of the bacteria undergoes a mutation, resulting in the bacteria being resistant to the antibiotic

The population is then exposed to the antibiotic, killing bacteria without the resistant allele

The resistant bacteria survive and reproduce without competition, passing on the allele that gives antibiotic resistance to their offspring

After some time, most organisms in the population will carry the antibiotic resistance allele

What is stabilizing selection?

Stabilizing selection favors individuals with alleles for characteristics towards the middle of the range so they are more likely to survive and reproduce. It occurs when the environment isn't changing and it reduces the range of possible characteristics.

Provide an example of stabilizing selection.

Human birth weight, where medium-sized babies are more likely to survive compared to very small or very large babies.

Explain how human birth weight is an example of stabilising selection

Humans have a range of birth weights

Very small babies are less likely to survive - partly because they find it hard to maintain their body temperature

Giving birth to large babies can be difficult so large babies are less likely to survive too

Conditions are most favourable for medium-sized babies - so weight of human babies tends to shift towards the middle of the range.

What is the outcome of natural selection over many generations?

The advantageous allele increases in frequency within the population.

What is speciation?

Speciation is the process where new species are produced, and they can no longer interbreed with the original species.

What is the relationship between allele frequency and survival?

Higher allele frequency of advantageous traits increases the likelihood of survival and reproduction in a population.

What role does environmental change play in directional selection?

Environmental change can favor individuals with extreme traits that are better suited to the new conditions.

Why are not all mutations advantageous?

Most mutations result in non-functional proteins that do not result in any survival benefit.