Biology B5 genetic

Q: What is variation?

The differences in characteristics between individuals of the same species.

What is evolution?

The gradual change in inherited characteristics of a population over generations.

Explain how natural selection can lead to evolution.

Individuals with advantageous characteristics are more likely to survive and reproduce, passing on these alleles. Over generations, these traits become more common.

A population of insects has variation in colour. Darker insects survive predation more often. Explain what happens over time.

Darker insects survive and reproduce more → more offspring inherit dark colour → population becomes mostly dark.

What is a mutation?

A change in the DNA sequence of an organism.

Name two types of mutations.

Gene mutations (change in a single gene) and chromosome mutations (change in whole chromosomes).

Explain how a mutation can be beneficial.

It can produce a new characteristic that improves survival or reproduction, which may be passed on.

What effect do most mutations have on the organism?

Most are neutral or harmful, causing no advantage or reducing survival.

What is meiosis?

A type of cell division that produces four genetically different gametes, each with half the number of chromosomes.

What is a gamete?

A sex cell (sperm or egg) with half the normal chromosome number.

What is a diploid cell?

A cell that contains two sets of chromosomes (one from each parent). Most body cells are diploid.

What is a haploid cell?

A cell that contains 1 of chromosomes (found in gametes). Most body cells are haploids

Explain why meiosis is important for sexual reproduction

It produces genetically varied gametes and maintains the chromosome number after fertilisation.

Describe the difference between meiosis and mitosis.

Meiosis produces 4 genetically different gametes with half chromosomes; mitosis produces 2 identical cells with full chromosomes.

What is sexual reproduction?

Reproduction involving the fusion of male and female gametes, producing genetically varied offspring.

What is asexual reproduction?

Reproduction without gametes, producing genetically identical offspring.

Give one example of sexual reproduction.

Humans, most plants, mammals.

Give one example of asexual reproduction.

Bacteria via binary fission, strawberries via runners.

State one advantage of sexual reproduction

Produces genetic variation, which helps adaptation to changing environments.

State one disadvantage of sexual reproduction.

Requires two parents, slower, fewer offspring.

State one advantage of asexual reproduction.

Only one parent needed, rapid reproduction, many offspring.

State one disadvantage of asexual reproduction.

No genetic variation → population vulnerable to disease or environmental change.

What is a genotype?

The genetic makeup of an organism (alleles present).

What is a phenotype?

The observable characteristics of an organism.

: Explain why offspring of two heterozygous parents show variation.

Different combinations of alleles from parents → different genotypes → different phenotypes.

Who was Mendel?

Gregor Mendel, father of genetics, discovered the principles of inheritance using pea plants.

What is a dominant allele?

An allele that is expressed even if only one copy is present.

What is a recessive allele?

An allele that is only expressed if two copies are present.

What is classification?

Grouping organisms based on shared characteristics.

: Why do scientists classify organisms?

To organise biodiversity, understand relationships, and make identification easier.

Give the correct order of classification from broadest to most specific.

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Explain why DNA analysis is used in modern classification.

It shows genetic relationships more accurately than physical characteristics alone.