Biology · Edexcel Paper 1
Reproduction, Meiosis and Variation
How gametes are made by meiosis, how asexual and sexual reproduction compare, and why individuals of the same species differ, from genetic and environmental causes to mutation. Matches Edexcel 3.1B to 3.3, 3.19, 3.20, 3.22 and 3.23. Every lesson is for both Combined Science and separate Biology at Foundation and Higher, except Asexual and Sexual Reproduction, which is for separate Biology only.
Lessons
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1
Meiosis and Gametes
Your body cells have 46 chromosomes, but a sperm or an egg has only 23. This lesson explains how a special type of cell division, meiosis, halves the…
9 terms -
2
Asexual and Sexual Reproduction
Some organisms reproduce with one parent and some need two. This lesson is for separate Biology only: Combined Science students do not need it. It compares the…
9 terms -
3
Causes of Variation
No two people are exactly alike. This lesson explains how genes and the environment each cause differences between individuals, and how to tell continuous…
10 terms -
4
Mutations and Genetic Variation
Every new allele began as a mutation. This lesson explains what mutations are, what causes them, why most of them do nothing, and why a population of a species…
9 terms
Key terms in this chapter
All 37, gathered from every lesson.
- Meiosis
- A type of cell division that produces four genetically different haploid gametes.
- Gamete
- A sex cell, such as a sperm or an egg, with half the number of chromosomes of a body cell.
- Haploid
- Having one set of chromosomes, as in a gamete.
- Diploid
- Having two sets of chromosomes, as in a body cell.
- Fertilisation
- The fusion of a male gamete and a female gamete.
- Zygote
- The cell formed when two gametes fuse. It is diploid.
- Sperm
- The male gamete in animals.
- Egg cell
- The female gamete in animals.
- Genetic variation
- Differences in the genes of individuals of the same species.
- Asexual reproduction
- Reproduction with one parent, in which the offspring are genetically identical to the parent.
- Sexual reproduction
- Reproduction involving the fusion of male and female gametes, which produces genetically different offspring.
- Clone
- An organism that is genetically identical to another.
- Variation
- The differences between individuals of the same species.
- Mate
- A partner for sexual reproduction.
- Reproductive cycle
- The time it takes an organism to reproduce.
- Pathogen
- A microorganism that causes disease.
- Population
- All of the individuals of one species living in a particular area.
- Runner
- A stem that grows along the ground from a plant and grows roots, making a new plant.
- Variation
- The differences between individuals of the same species.
- Genetic variation
- Differences in characteristics caused by differences in genes.
- Environmental variation
- Differences in characteristics caused by the environment, also called acquired characteristics.
- Phenotype
- The characteristics of an organism, caused by its genes and the environment.
- Continuous variation
- Variation in which a feature can take any value within a range.
- Discontinuous variation
- Variation in which a feature falls into distinct categories.
- Acquired characteristic
- A feature that an organism gains during its life, which is not inherited.
- Polygenic
- Controlled by many genes.
- Random sample
- A sample in which every individual has an equal chance of being chosen.
- Mutation
- A change in the DNA of a gene.
- Mutation
- A random change in the base sequence of DNA.
- Allele
- A different version of the same gene.
- Mutagen
- Something that increases the rate of mutation, such as ionising radiation or certain chemicals.
- Ionising radiation
- Radiation, such as X-rays and gamma rays, that can damage DNA.
- Genetic variation
- Differences in the genes of individuals in a species.
- Phenotype
- The observable characteristics of an organism.
- Neutral mutation
- A mutation that has no effect on the phenotype.
- Inherited
- Passed from parent to offspring in the genes.
- Antibiotic resistance
- The ability of bacteria to survive an antibiotic that would normally kill them.