Biology Form Four - Genetics, Evolution, and Coordination

Comprehensive practice questions covering high-school level Biology Form Four Genetics, Evolution, Coordination in plants and animals, and skeletal support.

How is 'Genetics' defined in the transcript?

The study of heredity and variation.

What is the difference between 'Heredity' and 'Variation'?

Heredity is the transmission of traits from parents to offspring, while variation refers to observable differences within organisms of the same species.

What is the primary difference between Discontinuous and Continuous variation?

Discontinuous variation shows distinct differences with no intermediates and is controlled by genes alone (e.g., blood groups), while Continuous variation shows a range from one extreme to another and is controlled by both genes and environment (e.g., height).

What are the three chemical components of a DNA nucleotide?

Pentose sugar (deoxyribose), a phosphate molecule, and a nitrogenous base.

In DNA base pairing, which nitrogenous bases always join together?

Adenine joins with Thymine ($A-T$) and Cytosine joins with Guanine ($C-G$).

What base replaces Thymine in an RNA molecule?

Uracil ($U$).

Define 'Genotype' versus 'Phenotype'.

Genotype is the genetic constitution of an organism (e.g., $TT$ or $tt$), while Phenotype is the physical appearance or observable trait.

What does 'Mendel's First Law (Law of Segregation)' state?

The characteristics of an organism are controlled by genes which occur in pairs, and only one of those genes is contained in a gamete.

Why did Gregor Mendel use garden peas (Pisum sativum) for his experiments?

They mature faster, naturally self-pollinate, produce many seeds, and have sharply contrasting characteristics.

What is the typical phenotypic ratio of a Mendelian F2 generation in a monohybrid cross?

$3:1$ (e.g., $3$ tall to $1$ short).

What happens in 'Co-dominance'?

Both alleles in a pair are dominant and both express themselves phenotypically in the offspring (e.g., ABO blood group system).

Who are considered 'Universal Donors' and 'Universal Recipients' in the ABO system?

Blood group O individuals are universal donors, and blood group AB individuals are universal recipients.

What is 'Erythroblastosis foetalis'?

A condition where a Rhesus negative mother’s antibodies destroy a Rhesus positive foetus’s red blood cells, often occurring in subsequent pregnancies.

How is sex determined in humans?

By sex chromosomes: females are $XX$ (homogametic) and males are $XY$ (heterogametic). Fusion of an ovum with a Y-bearing sperm results in a male child.

Why are sex-linked traits like Haemophilia more common in males?

They require only one recessive gene on the X chromosome to be expressed in males ($XY$), whereas females ($XX$) require two recessive genes.

What is 'Non-disjunction'?

The failure of homologous chromosomes to separate during meiosis, leading to gametes with too many or too few chromosomes.

What are the physical symptoms of Down's syndrome (Mongolism)?

Mental deficiency, thick tongue, slit eye appearance, cardiac malfunctions, short body, and stubby fingers.

Define 'Organic Evolution'.

The emergence of complex life forms from pre-existing simple life forms gradually over a long period of time.

What is the difference between 'Homologous' and 'Analogous' structures?

Homologous structures share a common embryonic origin but perform different functions (divergent evolution); analogous structures have different origins but perform similar functions (convergent evolution).

What is the central concept of Lamarck's Theory of Evolution?

The use and disuse of structures and the inheritance of acquired traits.

Name the four steps of Charles Darwin's Theory of Natural Selection.

1. Variation exists; 2. Overproduction of offspring; 3. Struggle for existence; 4. Survival of the fittest.

What is 'Industrial Melanism' as seen in Peppered Moths (Biston betularia)?

An example of natural selection where dark-colored moths gained a survival advantage over light-colored moths after tree trunks were darkened by soot during the industrial revolution.

What is a 'Stimulus'?

A condition in the environment which produces a change in the activity of part or the whole organism.

Define 'Phototropism' and specify which plant part is 'positively phototropic'.

Growth curvature in response to unidirectional light; shoot tips are positively phototropic.

How do auxins influence growth in plant shoot tips exposed to one-sided light?

Auxins migrate to the darker side, stimulating faster cell elongation there and causing the shoot to bend towards the light.

Name the three types of neurons in the animal nervous system.

Sensory (afferent) neuron, Motor (efferent) neuron, and Relay (intermediate) neuron.

What are the two major divisions of the Central Nervous System (CNS)?

The brain and the spinal cord.

What is the function of the Cerebellum?

Maintenance of body balance, posture, and dexterity in fine movements.

Define a 'Synapse'.

A gap between two adjacent neurons across which impulses are transmitted via chemicals like acetylcholine.

The hormone 'Adrenaline' is known as the 'fight or flight' hormone; what are three of its effects?

Increased heartbeat, faster breathing rate, and stimulation of conversion of glycogen to glucose in the liver.

What is the visual difference between the function of 'Cones' and 'Rods' in the retina?

Cones are responsible for bright light and color vision; rods are responsible for dim light vision.

How is Short-sightedness (Myopia) corrected?

By wearing spectacles with biconcave lenses to diverge light rays before they reach the eye lens.

Which part of the ear is responsible for equalizing air pressure between the middle ear and the atmosphere?

The Eustachian tube.

What are the three components of the mammalian axial skeleton?

The skull, the rib cage, and the vertebral column.

Identify the first two cervical vertebrae and their specific joint functions.

The first is the Atlas (allows nodding/up-and-down movement) and the second is the Axis (allows turning/rotary movement).

What are 'Antagonistic Muscles' in the context of movement?

A pair of muscles where one contracts while the other relaxes to bring about movement, such as the biceps and triceps.

What does it mean for 'Cardiac Muscle' to be 'myogenic'?

Its contraction originates from within itself without the need for external nervous or hormonal stimulation.

What is 'Tissue Culture' in plants an example of?

Cloning, which is a type of asexual reproduction where offspring are genetically identical to the parent.

What is 'DNA Fingerprinting' used for in legal issues?

Crime detection and settling disputed parentage based on unique base sequence patterns.