Theory of Evolution Glossary

A comprehensive set of Q&A flashcards covering key glossary terms and concepts from Ms. C.R. Els' lecture on the Theory of Evolution.

What is evolution?

The gradual change over time in living organisms.

How is biological evolution defined?

Genetic changes in a population inherited over successive generations—driven by natural selection, mutations, and genetic drift—resulting in new species.

What does macro-evolution describe?

Large-scale evolutionary changes over long periods that lead to the formation of new species.

What does micro-evolution refer to?

Small-scale evolutionary changes over short periods that alter allele frequencies within a population.

In science, what is a hypothesis?

An informed, evidence-based assumption that proposes an explanation or solution to a problem.

What is meant by a scientific theory?

A well-substantiated, repeatedly tested explanation that makes sense of natural phenomena.

What is the fossil record?

The cumulative list of all discovered fossils of varied ages documented by palaeontologists worldwide.

What are transitional fossils ("missing links")?

Fossils showing a mix of traits that link different evolutionary groups.

What does the phrase "modification by descent" mean?

Basic body plans became modified over generations to suit different environments.

What is a pentadactyl limb?

A vertebrate limb with five digits that may look different and perform different functions.

How is a homologous structure defined?

Similar anatomical structures with a shared body plan that perform different functions (e.g., vertebrate forelimbs).

What are analogous structures?

Body parts with the same function but different structures in unrelated organisms.

What does biogeography study?

The geographic distribution of extant and extinct plant and animal species.

What is a vestigial structure or organ?

A reduced physical structure that no longer serves its original function.

What is depicted by a phylogenetic tree?

Lines of evolutionary descent linking species or genes to a common ancestor.

What does Lamarckism propose?

That acquired characteristics of an organism are passed to its offspring.

What does gradualism suggest about evolution?

Species evolve slowly through small changes over long time periods.

What is punctuated equilibrium?

Long periods of little change punctuated by short bursts of rapid evolutionary change.

How is natural selection defined?

Environmental conditions favor the survival and reproduction of the best-adapted individuals.

What is artificial selection?

Human-directed breeding for desired traits that may not aid survival.

What is a species?

A group of organisms that can interbreed and produce fertile offspring.

What is speciation?

The formation of new species, increasing Earth’s biodiversity.

What is extinction?

The loss of a species, decreasing biodiversity.

Define population in evolutionary terms.

Individuals of the same species occupying a habitat and interbreeding freely.

What is a gene pool?

All alleles present in the reproductive individuals of a population.

Explain gene flow.

The exchange of alleles between populations.

What is reproductive isolation?

When populations can no longer interbreed, preventing gene flow and enabling speciation.

Define gene mutation.

A change in the DNA base sequence of a gene.

What is a harmful mutation?

A mutation producing a non-functional or shortened protein that harms or kills the organism.

What is a neutral mutation?

A DNA change with no effect on phenotype or fitness.

What is a beneficial mutation?

A DNA change that produces a new gene enhancing survival in a specific environment.

What is the founder effect?

Loss of genetic variation when a new population is started by a small group from the original population.

What is convergent evolution (convergence)?

Unrelated organisms independently evolving similar adaptations to comparable environments.

What is divergent evolution (divergence)?

One common ancestor producing various different but related species, evidenced by homologous structures.

What is geographic (allopatric) speciation?

Speciation that occurs when populations are separated by a physical barrier.

What is sympatric speciation?

Speciation occurring within the same geographic area without a physical barrier.

What is inbreeding?

Mating between genetically related individuals, increasing homozygosity.

What is outbreeding?

Mating between unrelated individuals, increasing heterozygosity.

What are prezygotic isolation mechanisms?

Barriers preventing mating or fertilisation before a zygote forms.

What is temporal (seasonal) isolation?

Different species breed at different times, preventing interbreeding.

What is behavioural isolation?

Species-specific courtship behaviours that prevent mating between different species.

What is mechanical isolation?

Structural differences (e.g., flower shape) preventing successful mating or pollination across species.

What are postzygotic isolation mechanisms?

Barriers after fertilisation that lead to inviable or sterile offspring.