Genetics and Evolution

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infoWhy this? Genetics explains how DNA, genes, and chromosomes transmit inherited characteristics, while variation and natural selection explain how populations change over time. These ideas help us define species, account for adaptation and extinction, and understand why conserving biodiversity matters.

scheduleWhy now? The unit draws together Year 7 learning about nuclei, specialised gametes, fertilisation, ecosystems, competition, and adaptation. Connecting cellular inheritance with population-level change provides a coherent progression from reproduction to evolution and biodiversity.

Characteristics are inherited from both parents through the genetic material (DNA) passed on in gametes during reproduction.
DNA is a molecule that carries genetic information.
Genes are sections of DNA containing instructions for proteins, which influence characteristics.
Chromosomes are long strands of DNA containing many genes.
Watson and Crick built the first accurate model of DNA's double helix structure, using data from Rosalind Franklin's X-ray diffraction images and Maurice Wilkins' work on DNA structure.
A species is a group of organisms that can interbreed and produce fertile offspring.
Examples of species include Homo sapiens (humans), Canis lupus (wolves), and Quercus robur (English oak).
Continuous variation refers to characteristics that show a range of values, such as height or mass, and is usually influenced by both genes and environment.
Discontinuous variation refers to characteristics that fall into distinct categories, such as blood group or tongue rolling, and is usually controlled by a single gene or a small number of genes.
Causes of continuous variation include genetic factors (multiple genes) and environmental influences.
Causes of discontinuous variation are mainly genetic, often involving one or a few genes.
Natural selection is the process by which species change over time; individuals with advantageous adaptations survive and reproduce, passing on beneficial traits.
Competition between species for resources such as food, space, or mates can lead to extinction if one species is outcompeted.
Extinction can occur due to lack of adaptation to changing environments or competition, leading to inability to survive and reproduce.
Biodiversity is the variety of living organisms in an ecosystem.
Maintaining biodiversity is important for ecosystem stability, resilience, and provision of resources.
Ways to maintain biodiversity include protecting habitats, creating nature reserves, captive breeding and reintroduction programmes, and legal protection of endangered species.

rocket_launchYou must be able to

Determine whether organisms belong to the same species by assessing their ability to interbreed and produce fertile offspring, and justify the reasoning.
Classify examples of variation within a species as continuous or discontinuous, and give examples of each.
Define continuous and discontinuous variation, and identify their causes in given examples.
Measure a trait, such as height or hand span, among individuals in the class, record the data, and represent the results using an appropriate graph, such as a bar chart for discontinuous variation or a histogram for continuous variation.
Describe, using examples, how a species has changed over time by natural selection, including the role of adaptation and survival of the fittest.
Explain, using examples, how competition and adaptation can lead to extinction.
Explain, using key terms, why maintaining biodiversity is important, and describe different methods used to conserve biodiversity.

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