UNIT 1 BIOLOGY IB

Evolution

Heritable

transmissible from parent to offspring

Evolution

the cumulative change in the characteristics of a population

Base pairs

a unit of DNA or RNA made of two chemical bases joined together by hydrogen bonds

Base sequence

the exact order of nitrogen-containing chemical blocks, called nucleotide bases, along a strand of DNA or RNA

Selective breeding

the process where humans choose specific plants or animals to mate

Natural selection

the process where plants and animals with traits best suited to their environment survive and have more babies

Alleles

a different form of a gene

Convergent evolution

when completely different species independently develop the same physical traits or behaviors because they live in similar environments or face identical survival challenges

Analogous

similar or comparable to something else in certain ways, even if they are different overall

Homologous (chromosomes and structures)

matching pairs of chromosomes that share the same length, shape, centromere position, and gene order

Non-homologous

the primary cellular pathway that repairs double-strand breaks in DNA by directly sticking the broken ends back together without needing a matching sequence template

Speciation

the evolutionary process where new and distinct species form from a single ancestral population

Sympatric

living or occurring in the same geographic area

Allopatric

occurring in separate geographic areas

Adaptive radiation

an evolutionary process where a single ancestral species rapidly diversifies into many new forms

Niche

a shallow recess in a wall, a specific market segment, an organism's role in an ecosystem, or a job/position well-suited to a person's abilities

Selection pressure

any external environmental factor that reduces or increases the reproductive success of certain organisms within a population, driving the process of natural selection

Interspecific

between different species

Intraspecific

within or between members of the same species

Polyploidy

a condition where a cell or organism has more than two complete sets of chromosomes

Hybridization

the mixing of atomic orbitals (such as s, p, and d) to form new, identical hybrid orbitals

Variation

a change different to the original

Mutation

a change in the base sequence

Abiotic

non-living

Biotic

living

Gene pool

he total collection of all genes, including all different gene forms, or alleles, in a single interbreeding population

Genetic drift

an evolutionary mechanism where allele frequencies in a population change over generations due to random chance instead of natural selection

Allele frequency

how often a specific gene variant appears in a group of individuals

Directional

a type of natural selection where an extreme phenotype is favored over all other phenotypes

Disruptive

a type of natural selection where extreme values for a trait are favored over intermediate values

Stabilizing

a type of natural selection where average traits are favored and extreme variations are rejected

Hardy-Weinberg

states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences

Binomial

the official system of naming living things

Karyotype

a complete set of chromosomes in an organism

Genome

the complete set of DNA instructions found in a living organism

Proteome

the entire set of proteins expressed by a genome, cell, tissue, or organism at a given time and under defined conditions

Clades

a group of living things that includes one single common ancestor and all of its descendants

Cladograms

Molecular phylogeny

the study of evolutionary links between living things