Biology EA

Species Richness

The number of different species in an area

Species Evenness

How relatively abundant each species is compared to other in the community

Lincoln Index

A formula used to estimate population size from capture-recapture data

Capture-recapture

A sampling technique for mobile animal populations: individuals are caught, marked, released, then recpatured to estimate population size

Quadrant Sampling

A technique using a square frame to sample stationary or slow-moving organisms in a defined area

Line Transect

A sampling technique where a line is laid across an environmental gradient and organisms touching it are recorded

Biotic Factos

Living components that affect an organism’s distribution/abundance, e.g., predation, competition, disease, food avaliability

Abiotc factors

Non-living physical/chemical factors like space, water, nutrients, shelter and envrionmental conditions

K-strategist

A species with slow reproduction, few offspring and high parental care, typically living near carrying capacity

r-strategist

A species with rapid reproduction, many offspring and minimal parental care, suited to unstable environments

Exponental growth (J-curve)

Population growth with an accelerating rate and no limiting factors, forming a J-shaped curve

Logistic growth (S-curve)

Growth that starts fast then levels off as it approaches carrying capacity, forming an S-shaped curve

Carrying capacity

The maximum population size an environment can sustainably support

Predation

An interaction where one organism (predator) kills and consumes another (prey)

Competition

An interaction where organisms compete for the same limited resource, to the detriment of both

Mutualism

A species interaction where both species benefit

Commensalism

A species interaction where one species benefits and the other is unaffected

Parasitism

A species interaction where one species (parasite) benefits at the expense of the other (host)

Ecological Niche

The role and position a species has in its environment, including how it meets its needs for food and shelter

Competitive exclusion principle

Two species with identical niches cannot coexist indefinitely; one will outcompete the other

Keystone Species

A species whose impact on community structure is disproportionately large relative to its abundance

Primary Sucession

Ecological development on newly exposed substrate with no existing soil or organisms, e.g. after a volcanic eruption

Secondary Sucession

Ecological recovery occurring after a disturbance in an area where soil and some organisms remain, e.g. after a fire

Pioneer Species

The first hardy species to colonise a bare or distributed environment

DNA Replication - Helicase

Unwinds the DNA double helix by breaking hydrogen bonds between base pairs

DNA Replication - DNA Polymerase

Synthesises new complementary DNA strands during replication

Meiosis

Cell division producing four genetically unique haploid cells through crossing over, independent assortment and random fertilisation

Point mutation

A change to a single nucleotide base in the DNA sequence

Frameshift Mutation

An insertion or deletion of nucleotide(s) that shifts the reading frame of a gene

Transcription

The copying of a gene's DNA sequence into messenger RNA in the nucleus

Translation

The synthesis of a polypeptide from mRNA at the ribosome, using tRNA, codons and anticodons

Heterochromatin

Tightly packed chromatin that is less accessible for transcription

Euchromatin

Loosely packed chromatin that is more transcriptionally active

HOX Genes

A family of transcription factor genes that regulate body plan and morphology during development

Recombinant DNA

DNA created by cutting a fragment with restriction enzymes and joining it into a plasmid using DNA ligase

PCR (polymerase chain reaction)

A technique that amplifies specific regions of DNA by repeated temperature cycling

Gel Electrophoresis

A technique that separates DNA fragments by size using an electric current, producing a banding pattern

Microevolution

Small changes in allele frequencies within a population, driven by mutation, gene flow and genetic drift

Macroevolution

Large-scale evolutionary patterns, such as speciation, arising from the accumulation of microevolutionary changes over long timescales

Genetic Drift

Random changes in allele frequencies, with a greater effect in small populations

Gene Flow

The transfer of alleles between populations through migration and interbreeding

Natural Selection - Stabilising Selection

Favours the average/intermediate phenotype, reducing variation

Natural Selection - Directional Selection

Favours one extreme phenotype, shifting the population in that direction

Natural Selection - Distruptive Selection

Favours both extreme phenotypes over the intermediate, increasing variation

Allopatric Speciation

Speciation occurring due to geographic isolation between populations

Sympatric Speciation

Speciation occurring without geographic separation, within the same area

Cladogram

A diagram showing hypothesised evolutionary relationships between species based on shared characteristics

Phylogram

A cladogram-like diagram where branch lengths represent the amount of evolutionary change or time

Comparative Genomics

Comparing DNA sequences between species to find evidence for evolutionary relationships and to date divergence