Biology - Natural Selection, Bottleneck Effect, Genetic Markers, Ratites

genetic diversity

the variety of alleles in a population

Natural Selection

Natural selection is the process whereby some alleles are more favors by others within a population. The organisms with these alleles are more likely to survive and pass their alleles onto their offspring. This causes the more favorable allele to increase in frequency within the population

What is the general process to answer Natural selection questions

1. A population of organisms shows differences in their physical traits for a specific characteristic.

2. The organisms that have the more desirable characteristic are more likely to survive and pass on their favorable alleles to their offspring (explain how they are able to survive.)

3. Overtime, the allele frequency within the population changes - the alleles that help the organism survive becomes more common

Bottleneck Effect

A sudden and dramatic reduction in population

What is the bottleneck effect

This occurs when there is a big reduction in population size which results in the loss of some alleles from that population. The gene pool becomes limited to the alleles that the few remaining indivduals have therefore there is a significant reduction in genetic diversity

What happens to the population after the size recovers from the bottleneck effect

After the population recovers much of the genetic diversity in the original population is lost although it can increased through mutation or outbreeding.

What is an adaptation

A trait that helps an organism survive better in its environment. They can be structural, behavioural and physiological

How do we differentiate between adaptations

Structural: part of the anatomy of the organism that helps it survive

Behavioural: an action that organism makes to help it survive

Physiological: an internal body process that helps the organism to survive in its environment

How does a small genome pose a risk due to the bottleneck effect (not that the total amount of DNA physically shrank, instead, the genetic diversity within the species genome became small.)

1. Reduced genetic diversity - with fewer alleles available species are less likely to survive environmental change such as changing rainfall, changing food supplies or new diseases entering the environment (higher risk of extinction)

2. Inbreeding risks - A smaller genome means that there is less genetic diversity within a population. When genetic variation is low, individuals are more likely to be closely related, which increases the chance of inbreeding. This raises the likelihood of harmful recessive alleles pairing up, which can lead to genetic disorders or weaknesses. As a result, the population experiences inbreeding depression, where overall health, fertility, and survival rates decrease.

Inbreeding

Inbreeding occurs when related individuals mate and pass on similar genes to their offspring

Inbreeding depression

The reduced biological survival of offspring that results from mating between genetically related individuals

What are genetic markers and what do they do

Genetic markers are specific sequences of DNA that scientists can use to identify a particular gene or location in the genome.

What is a DNA barcode

A short sequence of DNA that is used to identify a species.

What are DNA barcodes for

They are useful for telling species apart that look very similar since species can look the same yet their DNA barcodes will be similar but not identical.

They can also be used to identify specific species that are carrying desirable alleles that have for example an immunity from a specific disease or can also see individuals that have non-desirable alleles that should not be bred from

What are ratites

large flightless birds

What is a special feature of all ratites

The sternum

Why was it possible for Moa and Kiwi to become flightless after coming to New Zealand

1. Before human arrival there were no predators meaning there was no need to fly.

2.After arriving in New Zealand, kiwis and moas evolved adaptations to survive without mammalian predators. Both became flightless, which saved energy and suited a ground-based lifestyle. Moas grew very large to reach vegetation, while kiwis became nocturnal with strong legs for digging and foraging. Kiwis also developed a keen sense of smell and sensitive hearing to find food in the dark, compensating for their small eyes and poor vision. These changes helped them thrive in a predator-free environment.

3. DNA studies show there was mutations that affecting wing development as it was an advantage to have smaller wing and less developed muscles for flight