MSCE Biology flashcards

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

Prokaryotic cell

A cell with no nucleus or membrane-bound organelles, such as a bacterium; its DNA lies free in the cytoplasm and ribosomes are present.

Magnification formula

Magnification equals image size divided by actual size. Convert both measurements to the same unit before dividing, then express the answer as a whole number or ×.

Active transport

Movement of ions or molecules across a membrane against their concentration gradient using carrier proteins and energy from ATP, as in root hair cells absorbing minerals.

Nitrate ions in plants

Mineral ions absorbed by roots and used to make amino acids and proteins. Deficiency causes stunted growth and yellowing of older leaves.

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.

Balanced diet

A diet supplying carbohydrates and lipids for energy, proteins for growth and repair, vitamins and minerals, fibre and water in the correct proportions.

Alveolus adaptation

A tiny air sac in the lungs with a large total surface area, thin moist walls, and a rich blood supply that maintains a steep diffusion gradient for oxygen and carbon dioxide.

Transpiration

Loss of water vapour from leaves through stomata. Rate increases with temperature, wind, light intensity and low humidity, and decreases when stomata close.

Anaerobic respiration

Breakdown of glucose without oxygen, producing lactic acid in muscle cells or ethanol and carbon dioxide in yeast, releasing less energy than aerobic respiration.

Selective reabsorption

Process in the kidney tubule where useful substances such as glucose, amino acids and most water are returned to the blood, leaving wastes to be excreted in urine.

Negative feedback

A control mechanism in which a change is detected by receptors and an effector response reverses it, restoring the variable towards its set point.

Reflex arc

The pathway of an involuntary response: receptor, sensory neurone, relay neurone, motor neurone and effector, producing a rapid protective action.

Meiosis

Reduction division producing four haploid cells from one diploid cell, generating genetic variation through crossing over and independent assortment of chromosomes.

Ovulation

Release of a mature egg from an ovary, triggered by a surge in luteinising hormone (LH) around the middle of the menstrual cycle.

Seed germination requirements

Water to activate enzymes, oxygen for aerobic respiration, and a suitable warm temperature; light is needed by some but not all seeds.

Genotype and phenotype

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

Natural selection

Process where heritable variation exists, selection pressures favour certain phenotypes, and survivors pass favourable alleles to offspring, changing allele frequencies over generations.

Hardy-Weinberg equation

p + q = 1 and p squared + 2pq + q squared = 1, where p and q are allele frequencies and q squared is the frequency of homozygous recessives.

Trophic level

A feeding position in a food chain, such as producer or primary consumer. Only about ten percent of energy passes to the next level.

Eutrophication

Nutrient enrichment of water, often by fertiliser runoff, causing algal blooms; decomposers then deplete oxygen and aquatic animals die.

Carrying capacity

The maximum population size an ecosystem can sustain indefinitely, set by limiting resources such as food, water, space and shelter.

Vaccination

Introduction of antigens from a weakened or inactive pathogen so lymphocytes produce antibodies and memory cells, giving rapid protection on later exposure.

Antibiotic resistance

Bacteria with mutations that survive antibiotic treatment reproduce and pass resistance alleles on, so the population becomes harder to treat over time.

Monoclonal antibodies

Identical antibodies produced by a single clone of cells, used in diagnosis and in targeted treatments because they bind one specific antigen.

Osmosis

Net movement of water across a partially permeable membrane from higher to lower water potential, without energy input from the cell.

Water potential

A measure of the tendency of water to move; pure water has the highest value (0 kPa) and adding solutes makes the value more negative.

Mitosis stages

Prophase, metaphase, anaphase and telophase, producing two genetically identical diploid daughter cells for growth, repair and asexual reproduction.

Facilitated diffusion

Passive movement of substances down a concentration gradient through channel or carrier proteins in the membrane, requiring no ATP.

Enzyme digestion products

Amylase breaks starch to maltose, protease breaks proteins to amino acids, and lipase breaks lipids to fatty acids and glycerol in the digestive tract.

Villi adaptations

Finger-like projections of the small intestine with a large surface area, thin walls and a rich blood supply, speeding absorption of digested nutrients into the blood.

Vital capacity

The maximum volume of air a person can exhale after the deepest possible inhalation, measured with a spirometer and reduced by conditions such as emphysema.

Reliability in experiments

Consistency of results, improved by repeating measurements and calculating a mean; accuracy instead depends on calibrated instruments and correct technique.