IB Biology D - Continuity and Change Key Definitions

A non-living component of the environment, such as temperature, light, or water availability, that influences the survival and reproduction of organisms.

The acrosome reaction is the first step in fertilization. It allows a sperm to penetrate the egg's protective glycoprotein layer, called the zona pellucida, to reach the plasma membrane of the egg.

Adaptations are traits that increase an organism’s fitness in response to environmental factors.

Albedo ($\alpha$) measures the reflectivity of a surface.

An allele is a variation of a gene.

Allele frequency refers to how common a particular allele is within a population. It is expressed as a proportion or percentage of all alleles for a specific gene.

Alternative splicing is a process that enables a single gene to produce multiple protein variants.

Anthropogenic refers to changes in the environment caused by human activities.

An anticodon is a sequence of three nucleotides on a transfer RNA (tRNA) molecule that is complementary to a codon on a messenger RNA (mRNA) strand.

Aquaporins are specialized proteins that facilitate water movement across cell membranes.

Asexual reproduction is a process where a single parent produces offspring without the involvement of gametes (sperm and egg).

Valves located between the atria and ventricles that prevent the backflow of blood.

A base substitution is a gene mutation where one nucleotide in the DNA sequence is replaced by another.

Biochemical Oxygen Demand (BOD) measures the oxygen required by microorganisms to decompose organic matter.

Biomagnification is the increase in toxin concentration at each successive trophic level in a food chain.

A biotic factor is a living organism that shapes its environment.

A box-and-whisker plot is a graphical representation that summarizes a dataset by showing its spread and central tendency.

Carbon sequestration refers to the process of capturing and storing carbon dioxide (CO₂) from the atmosphere to mitigate the effects of climate change.

The cell cycle is a series of stages that a cell goes through to grow, replicate its DNA, and divide into two daughter cells.

The rapid increase in cell numbers through division, occurring at a faster rate than cell death.

The chi-squared test is a statistical method used to assess whether the occurrences of two species in a given area are due to chance or due to some form of association, possibly from ecological interactions like competition or mutualism.

Long strands of DNA, tightly coiled around histone proteins, carrying genes.

Long-term shifts in temperature, precipitation, and other environmental factors that can alter the conditions of an ecosystem.

A climax community is a stable, mature ecosystem that has reached equilibrium with its environment.