Life Sciences Grade 12 - Mind the Gap Study Guide

Flashcards covering key vocabulary and concepts from the Life Sciences Grade 12 Mind the Gap study guide.

Nucleic acids

DNA and RNA, made of nucleotides.

Nucleotide

Building block of nucleic acids, consisting of a phosphate group, sugar (deoxyribose or ribose), and a nitrogenous base (adenine, thymine, guanine, cytosine, or uracil).

DNA

Double-stranded molecule containing deoxyribose sugar and the nitrogenous base thymine.

RNA

Single-stranded molecule containing ribose sugar and the nitrogenous base uracil.

DNA replication

Process during which a DNA molecule makes an exact copy of itself during interphase before mitosis or meiosis.

DNA profiling

Arrangement of black bars representing DNA fragments unique to each person (except identical twins), used for identification purposes.

Protein synthesis

Process by which proteins are made in each cell of an organism, involving transcription and translation.

Transcription

Process in protein synthesis where DNA unwinds and one strand is used as a template to form mRNA in the nucleus.

Translation

Process in protein synthesis where tRNA brings specific amino acids to the mRNA on the ribosome in the cytoplasm to form a protein.

Meiosis

Type of cell division where a diploid cell divides twice to form four dissimilar haploid cells (sex cells).

Homologous chromosomes

A pair of chromosomes, one from the mother and one from the father, that have the same genes at the same locus.

Significance of meiosis

Reduces the number of chromosomes by half and introduces genetic variation through crossing over.

Non-disjunction

Abnormal meiosis where homologous chromosomes or sister chromatids do not separate correctly, leading to genetic disorders like Down Syndrome.

External fertilization

Sperm fertilizes the egg outside the body, usually in water.

Internal fertilization

Male deposits sperm inside the reproductive organs of the female.

Ovipary

Eggs are laid and hatching takes place outside the mother's body.

Vivipary

The young develop inside the uterus of the mother.

Ovovivipary

Young develop from eggs that are fertilized internally and retained within the mother's body until they hatch.

Amniote Egg

Embryo protected by the shell of the egg; egg consists of many extraembryonic membranes that serve different functions.

Precocial

Hatchlings are quite well-developed when they hatch – eyes open, able to move, able to feed.

Altricial

Hatchlings are poorly-developed when they hatch. Unable to feed on their own, cannot move.

Testosterone

Male hormone produced in the testes responsible for the development of male secondary sexual characteristics and maturation of sperm cells.

Oestrogen

Female hormone produced in the ovaries responsible for the development of female secondary sexual characteristics and thickening of the endometrium.

Progesterone

Female hormone produced by the corpus luteum that stimulates the endometrium for pregnancy.

Puberty

Period in humans in which they experience physical changes that is stimulated by hormones to be capable of sexual reproduction.

Menstrual cycle

Recurring series of changes in the female reproductive system that occur every month involving the ovaries (ovarian cycle) and uterus (uterine cycle).

Ovulation

Release of egg cell from a mature Graafian follicle in the ovary.

Fertilization

Fusion of egg cell and sperm cell to form a zygote.

Implantation

Embedding of the embryo (blastocyst) in the endometrium of the uterus.

Placenta

Structure formed from the villi growing into the tissue of the uterus, attached to the embryo by the umbilical cord.

Gestation

Period between fertilization and the birth of the baby.

Gene

Small portion of DNA coding for a particular characteristic.

Alleles

Alternative forms of a gene occupying the same locus on homologous chromosomes.

Genotype

Genetic composition of an organism.

Phenotype

Physical appearance of an organism.

Dominant allele

Allele that masks the expression of another allele in a heterozygous condition.

Recessive allele

Allele that is masked in a heterozygous condition and only expressed in a homozygous condition.

Heterozygous

Having two different alleles for a particular characteristic.

Homozygous

Having two identical alleles for a particular characteristic.

Monohybrid cross

Genetic cross involving only one characteristic or trait.

Complete dominance

Dominant allele masks the expression of a recessive allele in the heterozygous condition.

Incomplete dominance

Cross between two phenotypically different parents produces offspring with an intermediate phenotype.

Co-dominance

Genetic cross in which both alleles are equally expressed in the phenotype.

Sex-linked characteristics

Characteristics or traits carried on the sex chromosomes.

Karyotype

Number, shape, and arrangement of all chromosomes in the nucleus of a somatic cell.

Mutations

Any sudden unexpected change in the genetic structure of a cell.

Pedigree diagram

Diagram used to study the inheritance of characteristics in a family over generations.

Genetic engineering

Process of changing, transferring, or manipulating genes on DNA to produce a different organism.

Brain

Responsible for processing and transmitting information throughout the body, and coordinates body activities.

Cerebrum

Controls voluntary actions, receives and interprets sensations, and enables higher thought processes.

Cerebellum

Coordinates voluntary movements and maintains balance.

Medulla oblongata

Transmits nerve impulses between spinal cord and brain, and controls involuntary actions like heartbeat and breathing.

Hypothalamus

Control center for hunger, thirst, sleep, body temperature, and emotions.

Neurons

Specialized cells that transmit impulses throughout the body.

Reflex arc

Quick, automatic action involving the spinal cord to protect the body from harm.

Accommodation

Adjustment of the lens shape to see objects clearly, whether near or far.

Pupillary mechanism

Regulation of the amount of light entering the eye by adjusting the size of the pupil.

Endocrine system

System responsible for chemical coordination and regulation of activities inside the body using hormones.

Negative feedback

Mechanisms that operate to detect and correct imbalances in the internal environment to restore homeostasis.

Homeostasis

Process of maintaining a constant internal environment within the body.

Temperature regulation

Control of body temperature to keep it around 37°C, regulated by the hypothalamus and skin blood vessels and sweat glands.

Tropism

Growth or turning movement of a plant in response to an environmental stimulus.

Auxins

Hormones that affect plant growth and development, responsible for phototropism and geotropism.

Evolution

Changes to the inherited traits of a population through successive generations.

Natural selection

Process where organisms with favorable characteristics survive and reproduce, passing on their traits, as explained by Darwin.

Lamarck's theory

An outdated theory that involves the inheritance of acquired characteristics and the law of use and disuse.

Punctuated equilibrium

Evolutionary theory showing species evolving rapidly during short periods of time alternating with long periods or no change.

Speciation

Formation of new species when a population can no longer reproduce with the original species.

Out of Africa hypothesis

Theory stating that modern humans originated in Africa.

Phylogenetic tree

Diagram that represents the evolutionary relationships among organisms.

Biodiversity

The variety of plant and animal species on Earth that provides food, fresh water, and other resources.

Food security

Access, by all people at all times, to adequate, safe, and nutritious food for a healthy life.

Global warming

The increase in the average temperature of the Earth's surface due to rising levels of greenhouse gases.

Greenhouse effect

Absorption of infrared radiation from the Earth by greenhouse gasses to keep the Earth warm so that it can sustain life