Topic 7

Question 1

What is the genotype of an organism?

Answer 1

the genotype is the genetic constitution of an organism

meaning the specific set of alleles that it possesses.

For example, in humans, the genotype for blood type might be AA, AO, BB, BO, AB, or OO.

Question 2

What is the phenotype of an organism?

Answer 2

the phenotype is the observable characteristics or traits of an organism,

which result from the expression of its genotype and interaction with the environment.

For example, height can be influenced by both genetic factors and environmental factors like nutrition.

Question 3

True or False

A gene can have multiple alleles

Answer 3

True

A single gene can have multiple alleles.

For example, the gene controlling blood type in humans has three common alleles: I^A, I^B, and i.

Question 4

What are dominant, recessive, and codominant alleles?

Answer 4

Dominant alleles are expressed in the phenotype even if only one copy is present (e.g., B for brown eyes).

Recessive alleles are only expressed when two copies are present (e.g., b for blue eyes).

Codominant alleles are both expressed in the phenotype when present together (e.g., I^A and I^B in AB blood type).

Question 5

What does it mean for an organism to be homozygous or heterozygous at a specific locus?

Answer 5

Homozygous organisms have two identical alleles at a specific locus (e.g., BB or bb).

Heterozygous organisms have two different alleles at a specific locus (e.g., Bb).

Question 6

How do you use genetic diagrams to predict outcomes in monohybrid crosses?

Answer 6

In monohybrid crosses, you track the inheritance of a single characteristic (e.g., flower color).

A Punnett square is often used to show the possible genotypes of offspring from two parents,

based on the dominant and recessive alleles they carry.

Question 7

What is a dihybrid cross?

Answer 7

A dihybrid cross tracks the inheritance of two different characteristics (e.g., seed shape and color in peas).

It involves using a Punnett square to predict the combinations of alleles for both traits and their phenotypic ratios in the offspring.

Question 8

what is codominance?

Answer 8

in codominance, both alleles are expressed equally in the phenotype.

For example, in cattle, if the red allele (R) and white allele (W) are codominant,

the heterozygous RW genotype would result in roan cattle (a mix of red and white hair).

Question 9

What are sex-linked traits and how do they affect genetic crosses?

Answer 9

Sex-linked traits are associated with genes located on sex chromosomes (X or Y).

In humans, traits like red-green color blindness are X-linked.

Males (XY) are more likely to express X-linked recessive traits because they only have one X chromosome.

Question 10

What is autosomal linkage and how does it affect inheritance patterns?

Answer 10

Sex-linked traits are associated with genes located on sex chromosomes (X or Y).

In humans, traits like red-green color blindness are X-linked.

Males (XY) are more likely to express X-linked recessive traits because they only have one X chromosome.

Question 11

What is autosomal linkage and how does it affect inheritance patterns?

Answer 11

Autosomal linkage refers to genes located on the same chromosome (not sex chromosomes) that tend to be inherited together.

This reduces the variety of offspring genotypes compared to unlinked genes,

because linked genes do not assort independently.

Question 12

what is epistasis?

Answer 12

Epistasis occurs when one gene masks or suppresses the expression of another gene.

For example, in mice, one gene determines if pigment will be produced, while another gene controls the pigment’s color.

If the first gene blocks pigment production, the mouse will be albino, regardless of the second gene’s alleles.

Question 13

What is the purpose of the chi-squared test in genetic studies?

Answer 13

The chi-squared (X²) test is used to compare observed phenotypic ratios from a genetic cross with expected ratios.

This helps determine if any deviations from expected results are due to chance or other factors, like linkage or epistasis.

Question 14

How do species exist in nature?

Answer 14

Species exist as one or more populations.

Each population consists of organisms of the same species living in a particular space and time, with the potential to interbreed.

For example, different populations of a bird species may be found in various regions, yet all belong to the same species.

Question 15

Define a population in biological terms.

Answer 15

A population is a group of organisms of the same species occupying a particular space at a particular time, capable of interbreeding.

For example, a population of fish in a specific lake or a group of deer in a forest.

Question 16

What is a gene pool?

Answer 16

A gene pool refers to the total collection of different alleles present in a population’s genetic makeup.

The gene pool contains all the possible alleles for every gene within the population.

Question 17

What is allele frequency?

Answer 17

Allele frequency is the proportion of a specific allele within the gene pool of a population.

For example, if a population has two alleles (A and a) for a gene, and 70% of the alleles are A, the allele frequency of A is 0.7.

Question 18

What does the Hardy-Weinberg principle state?

Answer 18

The Hardy-Weinberg principle is a mathematical model

that predicts allele frequencies in a population will remain constant from generation to generation,

assuming certain conditions are met, such as

no mutation, random mating, no gene flow, infinite population size, and no selection.

Question 19

What conditions must be met for the Hardy-Weinberg principle to apply?

Answer 19

The conditions include:

1. No mutations (allele frequencies are not altered by mutations).
2. Random mating (individuals pair by chance, not by phenotype or genotype).
3. No gene flow (no migration of individuals in or out of the population).
4. Large population size (to minimize random changes in allele frequencies).

5.No natural selection (all genotypes must have equal reproductive success).

Question 20

How do you calculate allele, genotype, and phenotype frequencies using the Hardy-Weinberg equation?

Answer 20

the Hardy-Weinberg equation is
p² + 2pq + q² = 1. Here:

p² represents the frequency of the homozygous dominant genotype.

2pq represents the frequency of the heterozygous genotype.

q² represents the frequency of the homozygous recessive genotype.

p is the frequency of the dominant allele, and q is the frequency of the recessive allele.

For example, if p = 0.7 and q = 0.3, then p² = 0.49, 2pq = 0.42, and q² = 0.09.

Question 21

Why do individuals within a population of a species show a wide range of variation in phenotype?

Answer 21

Variation in phenotype is due to both genetic and environmental factors.

The primary source of genetic variation is mutation,

while meiosis and random fertilisation during sexual reproduction add further genetic variation.

Environmental factors such as diet, climate, and exposure to different conditions also influence phenotype.

Question 22

How does meiosis contribute to genetic variation?

Answer 22

Meiosis introduces genetic variation through processes such as

crossing over (exchange of genetic material between homologous chromosomes) and independent assortment (random separation of chromosomes),

which produce unique combinations of alleles in gametes.

Question 23

What role does random fertilisation play in genetic variation?

Answer 23

Random fertilisation combines the unique gametes from two parents,

resulting in offspring with a genetic makeup different from both parents.

This randomness further increases the genetic diversity within a population.

Question 24

How does natural selection work?

Answer 24

Natural selection occurs when predation, disease, and competition for survival resources result in differential survival and reproduction.

Organisms with phenotypes that provide selective advantages (e.g., better camouflage or resistance to disease)

are more likely to survive, reproduce, and pass on favourable alleles to the next generation.

Question 25

How does natural selection affect allele frequencies within a gene pool?

Answer 25

Natural selection causes favourable alleles to increase in frequency

within a gene pool because individuals with those alleles are more likely to reproduce.

Conversely, alleles that do not confer an advantage may decrease in frequency over generations.

Question 26

What are stabilising, directional, and disruptive selection?

Answer 26

Stabilising selection favours the average phenotype, reducing variation (e.g., human birth weights).

Directional selection favours one extreme phenotype, leading to a shift in allele frequency (e.g., antibiotic resistance in bacteria).

Disruptive selection favours both extremes over the average phenotype, potentially leading to speciation (e.g., bird beak sizes for different food sources).

Question 27

What is evolution in biological terms?

Answer 27

Evolution is the change in allele frequencies in a population over time.

This can result from mechanisms such as natural selection, genetic drift, mutation, and gene flow.

Question 28

How does reproductive isolation lead to speciation?

Answer 28

Reproductive isolation occurs when two populations of the same species become separated
(e.g., geographically or behaviourally).

Over time, genetic differences accumulate due to mutations and selection pressures.

If these differences become significant enough to prevent interbreeding and the production of fertile offspring, new species arise.

Question 29

What is the difference between allopatric and sympatric speciation?

Answer 29

Allopatric speciation occurs when populations are geographically separated, leading to genetic divergence.

Sympatric speciation occurs within the same geographic area, often due to factors such as different ecological niches or behavioural isolation, resulting in reproductive separation.

Question 30

Why is genetic drift more important in small populations?

Answer 30

Genetic drift has a more significant impact in small populations

because random changes in allele frequencies can lead to the loss of alleles more quickly.

In larger populations, random fluctuations tend to balance out, but in small populations,

these changes can dramatically affect genetic diversity.

Question 31

How do natural selection and isolation lead to the formation of new species?

Answer 31

Natural selection acts on isolated populations by favouring individuals with advantageous traits for their specific environments.

Over time, these populations diverge genetically due to different selection pressures.

If the divergence is sufficient, they become reproductively isolated, forming new species.

Question 32

How has evolutionary change over a long period resulted in species diversity?

Answer 32

Over long periods, evolutionary processes like natural selection,

mutation, and genetic drift cause gradual changes in allele frequencies.

Combined with speciation events, these processes lead to the emergence of new species,

contributing to the vast diversity of life observed today.

Question 33

What forms a community in an ecosystem?

Answer 33

Populations of different species form a community.

A community, together with the non-living (abiotic) components of its environment, forms an ecosystem.

Ecosystems can vary greatly in size, from small, like a pond, to large, like a rainforest.

Question 34

What is a niche within a habitat?

Answer 34

A niche is the role or position a species occupies within a habitat,

governed by its adaptations to both abiotic (non-living) and biotic (living) conditions.

It includes how the species interacts with other organisms and its environment,

such as food sources, predation, and reproduction.

Question 35

What is carrying capacity in an ecosystem?

Answer 35

Carrying capacity is the maximum population size of a species that an ecosystem can support,

given the available resources such as food, water, and shelter.

This size can vary due to factors like predation, competition, and environmental conditions.

Question 36

What are the two main types of competition within a population?

Answer 36

Intraspecific competition occurs between individuals of the same species for resources like food or mates.

Interspecific competition occurs between individuals of different species competing for the same resources, like light or space.

Question 37

How can the size of a population be estimated for non-motile organisms?

Answer 37

Population size can be estimated using:

Randomly placed quadrats to sample a population in a defined area.

Quadrats along a belt transect to study population changes along an environmental gradient, such as light or moisture.

Question 38

How is the population of motile organisms estimated using the mark-release-recapture method?

Answer 38

he mark-release-recapture method involves capturing individuals, marking them, releasing them back into the population, and then recapturing individuals after some time. The population size is estimated using the formula:

Estimatedpopulation=
Numberofmarkedindividualsrecaptured
(Numberofindividualsinfirstsample)×(Numberofindividualsinsecondsample)
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Question 39

What is primary succession?

Answer 39

Primary succession is the process of ecosystem development starting from bare substrate (e.g., bare rock) with no soil.

It begins with colonization by pioneer species (e.g., lichens),

followed by the establishment of more complex plant species until a climax community (a stable and mature ecosystem) is reached.

Question 40

How do species change the environment during succession?

Answer 40

As succession progresses, species modify the abiotic environment, often making it less hostile.

For example, pioneer species break down rock into soil,

allowing other species to colonize. New species may outcompete earlier colonizers,

leading to changes in community structure and increased biodiversity.

Question 41

Why is conservation of habitats often linked to managing succession?

Answer 41

Conservation often involves managing succession to maintain specific habitats.

For example, if succession is left unmanaged, a grassland may transition into woodland.

Conservationists may intervene (e.g., through grazing or cutting) to prevent this, thereby preserving the habitat and its biodiversity.

Question 42

Why is it important to balance human needs with conservation efforts?

Answer 42

Balancing human needs with conservation is crucial for sustainability.

Human activities like agriculture, urban development,

and resource extraction can conflict with conservation goals.

Effective management ensures that natural resources are preserved for future generations while meeting current human demands.

Question 43

How can evidence and data be evaluated in conservation efforts?

Answer 43

In conservation, it is important to critically evaluate data on species populations,

habitat conditions, and environmental changes.

Conflicting evidence may arise from different methodologies, ecological perspectives, or interests,

and must be considered to make informed decisions that balance ecological preservation and human activities.