NSSCO Biology 6116 flashcards

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

Independent variable

The factor deliberately changed by the investigator in an experiment; when it is continuous it is plotted on the x-axis of a graph.

Control group

A group in an experiment that receives no treatment or a placebo, providing a baseline for comparison with the experimental group.

Magnification formula

Magnification equals image size divided by actual size; convert both measurements to the same unit (1 mm = 1000 micrometres) before dividing.

Osmosis

The net diffusion of water through a partially permeable membrane from a region of higher water potential (dilute solution) to lower water potential (concentrated solution).

Active transport

Movement of ions or molecules across a cell membrane against their concentration gradient, using carrier proteins and energy released by respiration.

Mitosis

Nuclear division that produces two genetically identical diploid daughter cells; used for growth, repair and asexual reproduction in eukaryotes.

Plasmolysis

Shrinkage of the cytoplasm and vacuole away from the cell wall when a plant cell loses water by osmosis in a concentrated solution.

Photosynthesis equation

Carbon dioxide and water are converted into glucose and oxygen using light energy trapped by chlorophyll: 6CO2 + 6H2O gives C6H12O6 + 6O2.

Limiting factor

The factor in shortest supply that restricts the rate of a process such as photosynthesis; increasing it raises the rate until another factor becomes limiting.

Bile

Alkaline liquid made in the liver and stored in the gall bladder; it emulsifies fats into small droplets and neutralises acid from the stomach.

Aerobic respiration

Glucose plus oxygen produces carbon dioxide, water and energy; it occurs mainly in mitochondria and releases much more energy per glucose molecule than anaerobic respiration.

Alveoli adaptations

Microscopic air sacs in the lungs with a large total surface area, thin moist walls, dense capillary network and short diffusion distance for efficient gas exchange.

Tidal volume

The volume of air breathed in or out during one normal breath at rest; it is measured using a spirometer trace.

Transpiration

Loss of water vapour from the aerial parts of a plant, mainly through stomata; it creates the pull that draws water up the xylem.

Xylem tissue

Dead, hollow, lignified cells forming tubes that transport water and dissolved mineral ions from roots to leaves; flow is one-way and driven by transpiration.

Double circulation

Blood passes through the heart twice per complete circuit: the pulmonary circulation to the lungs and the systemic circulation to the body.

Homeostasis

Maintenance of a stable internal environment, including temperature, water, glucose and pH, around set points by negative feedback mechanisms.

ADH action

Antidiuretic hormone released by the pituitary gland increases water reabsorption in the kidney collecting ducts, producing smaller volumes of more concentrated urine.

Vasodilation

Widening of skin arterioles near the body surface, increasing blood flow and heat loss by radiation; this is a response to overheating.

Reflex arc

The route of a reflex: receptor, sensory neurone, relay neurone in the spinal cord, motor neurone and effector; reflexes are rapid and involuntary.

Synapse

A junction between two neurones where a neurotransmitter diffuses across the gap to carry the impulse from one cell to the next.

Auxin

A plant hormone made in shoot tips; it accumulates on the shaded side and stimulates cell elongation, causing shoots to bend towards light.

Pollination

Transfer of pollen from anther to stigma by wind, insects or other animals; it precedes fertilisation and may be self-pollination or cross-pollination.

Placenta function

Organ in the uterus where maternal and fetal blood exchange oxygen, nutrients, antibodies and waste across a thin membrane without the two bloods mixing.

Ovulation

Release of a mature egg from an ovary about 14 days into a 28-day menstrual cycle, triggered by a surge in luteinising hormone.

Natural selection

Individuals with inherited variations best suited to the environment survive, reproduce and pass on their alleles, so favourable allele frequencies increase over generations.

Genotype and phenotype

Genotype is the combination of alleles an organism carries; phenotype is the observable characteristics produced by the genotype interacting with the environment.

Monohybrid cross ratio

A cross between two heterozygotes such as Bb × Bb gives a 3:1 phenotype ratio and a 1:2:1 genotype ratio in the offspring.

Sex determination

Human sex is determined by sex chromosomes: XX is female and XY is male; the sperm, carrying X or Y, determines the sex of the offspring.

Eutrophication

Enrichment of water with nitrate or phosphate from fertiliser run-off, causing algal blooms, then decomposition that uses up oxygen and kills aquatic animals.

Quadrat sampling

A square frame placed at random to count organisms in a known area; results are scaled to estimate population size and repeats improve reliability.

Nitrogen fixation

Conversion of atmospheric nitrogen gas into nitrogen compounds by Rhizobium bacteria in root nodules or by lightning; plants then absorb nitrates from the soil.