DC CAPE 2.0 Science Biology flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Cell membrane structure

A phospholipid bilayer with embedded proteins and cholesterol. It is selectively permeable, letting small nonpolar molecules pass while ions and large polar molecules need channels or transporters.

Mitochondrion function

The organelle where aerobic respiration occurs. Its inner membrane hosts the electron transport chain, producing most of the cell's ATP from glucose and oxygen.

Enzyme denaturation

Loss of an enzyme's three-dimensional shape from heat or extreme pH. The active site no longer fits the substrate, so reaction rate drops sharply and cannot be restored by cooling.

Osmosis direction

Net movement of water across a semipermeable membrane from lower to higher solute concentration. Cells shrink in hypertonic solutions and swell or burst in hypotonic ones.

Transcription versus translation

Transcription copies DNA into mRNA in the nucleus; translation reads mRNA codons at ribosomes to assemble amino acids into a polypeptide chain.

Prokaryote versus eukaryote

Prokaryotes lack a membrane-bound nucleus and organelles and have circular DNA; eukaryotes have a nucleus, membrane-bound organelles, and linear chromosomes.

ATP role in cells

ATP is the universal energy currency: breaking its terminal phosphate bond releases energy that powers transport, synthesis, and movement, and it is regenerated by respiration.

Mendel's law of segregation

During meiosis the two alleles of a gene separate, so each gamete receives only one allele. Fertilization then restores two alleles in the offspring.

Test cross purpose

Crossing an organism of unknown genotype with a homozygous recessive individual. Offspring ratios reveal whether the unknown parent was homozygous dominant or heterozygous.

Codominance versus incomplete dominance

In codominance both alleles are fully expressed (AB blood type); in incomplete dominance the heterozygote shows a blended intermediate phenotype (red plus white gives pink).

Frameshift mutation effect

An insertion or deletion of bases not in multiples of three shifts the reading frame, altering every downstream codon and usually producing a nonfunctional protein.

Sex-linked trait inheritance

A trait whose gene lies on the X chromosome. Recessive X-linked disorders appear more often in males because they carry only one X and no second copy to mask it.

Genotype versus phenotype

Genotype is an organism's actual allele combination; phenotype is the observable trait produced by that genotype interacting with the environment.

Nondisjunction outcome

Failure of chromosomes to separate properly during meiosis, producing gametes with extra or missing chromosomes and causing conditions such as trisomy 21.

Punnett square use

A grid predicting genotype probabilities of offspring from parental alleles. Count boxes with each genotype and divide by total boxes to get expected ratios.

Natural selection requirements

Heritable variation, environmental pressure, and differential reproductive success. Individuals with favorable phenotypes reproduce more, raising those alleles' frequency over generations.

Evolutionary fitness meaning

An organism's reproductive success in its environment, measured by surviving offspring produced, not by strength, size, or lifespan.

Homologous versus analogous structures

Homologous structures share common ancestry despite different functions (human arm, bat wing); analogous structures share function but not ancestry (bird and insect wings).

Hardy-Weinberg conditions

No mutation, no migration, no natural selection, random mating, and a large population. When these hold, allele and genotype frequencies stay constant across generations.

Genetic drift definition

Random change in allele frequencies between generations, strongest in small populations. It is not driven by fitness and can eliminate beneficial alleles by chance.

Reproductive isolation

Any barrier preventing members of two populations from interbreeding and producing fertile offspring, which allows the populations to diverge into separate species.

Stabilizing selection

Selection favoring intermediate phenotypes and acting against both extremes, which reduces variation and keeps a trait's mean value unchanged.

Binomial nomenclature

A two-part scientific name: capitalized genus followed by lowercase species, both italicized. It gives every species one universally recognized name.

Three domains of life

Bacteria and Archaea are prokaryotic; Eukarya includes protists, fungi, plants, and animals. Archaea differ from Bacteria in cell wall and membrane chemistry.

Virus classification status

Viruses are acellular obligate parasites with nucleic acid inside a protein capsid. They lack metabolism and are not placed within the three domains of life.

Fungi nutrition mode

Fungi are heterotrophs with chitin cell walls that secrete enzymes and absorb digested nutrients externally, then reproduce by releasing spores.

Angiosperm versus gymnosperm

Angiosperms produce flowers and seeds enclosed in fruit; gymnosperms produce naked seeds usually in cones. Both are vascular seed plants.

Dichotomous key function

A tool that identifies organisms through a series of paired contrasting statements; each choice eliminates alternatives until one taxon remains.

Ten percent energy rule

Only about 10% of energy at one trophic level transfers to the next; the rest is lost as heat and in waste, limiting food chains to a few levels.

Carrying capacity

The maximum population size an environment can sustain given food, water, space, and other resources. Logistic growth levels off at this value.

Symbiosis types

Mutualism benefits both species, commensalism benefits one without affecting the other, and parasitism benefits one while harming the host.

Primary versus secondary succession

Primary succession begins on bare rock or lava with pioneer species and no soil; secondary succession follows disturbance where soil and seeds already exist, so it is faster.

Negative feedback loop

A control mechanism in which a change triggers a response that reverses it, such as insulin lowering high blood glucose to restore homeostasis.