Evolution: Formation of a New Species - Grade 12 Life Sciences Flashcards

40 practice flashcards covering key terms and concepts from Evolution, Variation, Speciation, reproductive isolation, and related examples from the Grade 12 Life Sciences notes.

What is the Biological species?

A group of organisms of common ancestry that closely resemble each other and have the ability to interbreed randomly and produce fertile offspring.

What is a Population?

A group of organisms of the same species that live in the same habitat at the same time and has the ability to interbreed randomly to produce fertile offspring.

What is a Gene pool?

The total number of alleles of all the reproductive individuals in a population.

What is Gene flow?

The exchange of alleles between populations.

What is Variation?

The small differences that are found within a population or species.

What is Speciation?

The formation of a new species that increases the biodiversity on Earth.

What are the two types of variation?

Continuous variation and Discontinuous variation.

What characterizes Continuous variation?

There is a range of different phenotypes for a trait; forms a continuous spectrum; the trait may be polygenic with multiple alleles; more alleles yield greater variety.

What characterizes Discontinuous variation?

Phenotypes fit into separate categories with no intermediate forms; only a single pair of alleles; fewer alleles lead to fewer possibilities; example: blood groups.

Give an example of Continuous variation.

Height in humans (a range of heights from short to tall).

How can continuous variation values be plotted?

Using a histogram or line graph; a histogram shows a bell-shaped curve; the environment can influence the values.

How can discontinuous variation values be plotted?

Using a bar graph; there is no bell-shaped curve because values are exact categories.

Does the environment influence continuous variation?

Yes, it can influence the values.

Does the environment influence discontinuous variation?

No, the environment does not influence these characteristics.

Causes of genetic variation?

Genetic recombination and mutations (including meiosis crossing over, independent assortment, sexual reproduction, random mating, random fusion of gametes) and mutations.

What is Genetic recombination?

Meiosis crossing over during Prophase I and random assortment of chromosomes during Metaphase; plus sexual reproduction, random mating, and random fusion of gametes.

What are Mutations?

The most important cause of genetic variation; gene mutations (insertion, deletion, substitution) with harmful, neutral, or beneficial effects; chromosome mutations (change in chromosome number).

What is the Founder effect?

Loss of variation when a new population is formed by a small number of individuals; the gene pool consists only of founder members' genes.

What is the Bottleneck effect?

A sharp reduction in population size that reduces genetic variation; the gene pool becomes smaller.

What is Inbreeding?

Crossing of closely related individuals; reduces genotypic and phenotypic variation; increases homozygosity; can lead to disease.

Advantages of inbreeding?

Produces predictable offspring; recessive genes can be isolated; undesirable traits can be isolated.

Disadvantages of inbreeding?

Offspring more susceptible to disease; high mortality; increase in abnormalities; recessive diseases become evident; loss of vigor; decrease in heterozygous genes; offspring can be infertile; gene pool becomes smaller.

What is Outbreeding?

Crossing of unrelated individuals; increases heterozygosity and variation.

Advantages of Outbreeding?

New characteristics introduced; genetic variation increases; gene pool enlarges; reintroduction of lost characteristics; increased hybrid vigour in offspring.

Types of speciation?

Allopatric speciation and Sympatric speciation.

What is Allopatric speciation?

Formation of two or more new species because of the separation of the original species by a geographical/physical barrier.

What is Sympatric speciation?

Formation of two or more new species without the presence of a geographical barrier.

What is Extinction?

The process by which all individuals of a particular species die out so that not even a single one exists.

What are reproductive isolating mechanisms?

Factors that prevent two species from producing viable, fertile offspring.

Prezygotic vs Postzygotic isolation?

Prezygotic isolation – before fertilization; Postzygotic isolation – after fertilization (abnormal development, no viable offspring).

Examples of prezygotic isolation?

Temporal isolation (breeding at different times of the year) and Behavioral isolation (species-specific courtship behaviour).

Temporal isolation?

Breeding at different times of the year.

Behavioral isolation?

Species-specific courtship behaviour; mating may be prevented if the behaviour is not recognized.

Adaptation to different pollinators?

Plants of closely related species have slightly different structures to attract different pollinators, preventing cross-pollination and increasing fertilisation success.

Reproductive isolating barriers?

Factors that prevent two species from producing viable, fertile offspring (includes prezygotic and postzygotic barriers).

Convergent evolution?

Different unrelated organisms that are independently adapting for similar environments.

Divergent evolution?

One common ancestor giving rise to different, but related organisms.

Polyploidy in plants?

An increase in chromosome number creates a new species in the same geographical area; crossbreeding cannot occur because chromosomes cannot form matching homologous pairs for meiosis.

Hybrid species?

Breeding of unrelated species can lead to a new species; not very common in nature.

Galapagos finches example of allopatric speciation?

Founding populations arrive, geographic isolation occurs, gene pool changes, reproductive isolation develops, ecological competition influences further evolution, leading to new species.