Producing New Cells
What are chromatids, and where are they found during mitosis?
Chromatids are identical copies of a chromosome that are joined together by a centromere. They are found after the chromosomes shorten and thicken.
What are the three types of neurons in the nervous system?
Sensory neurons, interneurons, and motor neurons.
What is the difference between diploid and haploid cells?
Diploid cells have two sets of chromosomes (one from each parent), while haploid cells have only one set of chromosomes.
Q: What is the difference between discrete variation and continuous variation?
A: Discrete variation involves traits controlled by a single gene (e.g., blood type), while continuous variation involves traits controlled by multiple genes (e.g., height or skin color).
Q: What are the three main plant organs involved in transport?
A: The three main plant organs are the roots, stems, and leaves.
What is the main purpose of mitosis in organisms?
Mitosis provides new cells for growth, repair of damaged tissues, and replacement of dead or damaged cells. It also maintains the diploid chromosome complement.
What is the function of the cerebellum in the brain?
The cerebellum is responsible for coordinating voluntary movements, balance, and posture.
Q: What are gametes, and what is their role in reproduction?
A: Gametes are reproductive cells (sperm in males and eggs in females) that are haploid. They combine during fertilisation to form a diploid zygote.
Q: Define the terms genotype and phenotype.
A: Genotype refers to the genetic makeup of an organism (the alleles it carries), while phenotype refers to the physical appearance or characteristics of the organism, determined by its genotype.
Q: Where does water enter the plant, and how is it transported?
A: Water and minerals enter the plant through the root hairs and are transported through the plant in dead xylem vessels.
Describe the role of stem cells in growth and repair.
Stem cells are unspecialised cells that can divide to self-renew. They have the potential to become different types of cells and are involved in the growth and repair of tissues.
Explain how electrical impulses travel along neurons.
Electrical impulses are carried along neurons through an action potential. The impulse travels down the axon and is transferred to the next neuron at the synapse through chemical signals.
Q: Describe the structure of a sperm cell.
A: A sperm cell has a head (containing the nucleus with DNA), a midpiece (packed with mitochondria to provide energy), and a tail (flagellum) for movement.
Q: What is the difference between homozygous and heterozygous?
A: Homozygous means having two identical alleles for a particular gene, while heterozygous means having two different alleles for the gene.
Q: What factors affect the rate of transpiration in plants?
A: Wind speed, humidity, temperature, and surface area all affect the rate of transpiration.
What is cell differentiation, and why is it important in the formation of tissues and organs?
Cell differentiation is the process by which unspecialised cells become specialised to perform specific functions. It is important because it allows the formation of different types of cells, tissues, and organs, which work together to form systems in the body.
How does the endocrine system control blood glucose levels?
The pancreas releases insulin to lower blood glucose levels and glucagon to raise blood glucose levels. Insulin helps cells take in glucose, and glucagon stimulates the liver to release glucose.
Q: What happens during fertilisation?
A: Fertilization is the fusion of the nuclei of two haploid gametes (sperm and egg) to form a diploid zygote, which then divides to form an embryo.
Q: What is a monohybrid cross, and how is it used in genetics?
A: A monohybrid cross is the mating of two individuals with different alleles for one trait. It is used to predict the probability of offspring inheriting certain alleles.
Q: Explain the structure and function of phloem tissue in plants.
A: Phloem tissue consists of living cells that transport sugars and other organic compounds up and down the plant to areas that need them.
Q: Explain the sequence of events in mitosis and describe the roles of chromatids, equator, and spindle fibres during this process.
1. Chromosomes shorten and thicken and become visible and chromatids. Nuclear membrane breaks down and spindle fibres form.
2. Chromatids line up along the equator of the cell.
3. Spindle fibres pull the chromatids apart, moving them to opposite sides of the cell.
4. Nuclear membrane reforms around the separated chromatids.
5. The cell divides into 2 identical daughter cells.
Q: Describe the structure and function of the reflex arc, including all parts involved and their roles in a reflex action.
A reflex arc is the pathway taken by nerve impulses in a reflex action, which occurs automatically and quickly:
Receptor: Detects a stimulus (e.g., pain).
Sensory Neuron: Carries the impulse to the spinal cord.
Interneuron: Relays the impulse within the spinal cord to the motor neuron.
Motor Neuron: Carries the impulse to an effector (e.g., muscles).
Effector: The muscle or gland that responds to the stimulus (e.g., pulling away from a hot surface). The reflex arc bypasses the brain, ensuring a quick response.
Q: Describe the process of fertilisation in humans, from the moment sperm and egg meet to the formation of the zygote.
Fertilization is the fusion of the male and female gametes:
Sperm: The sperm travels through the female reproductive system to reach the egg in the fallopian tube.
Egg: The egg is released during ovulation from the ovary and waits for sperm to reach it.
Fusion of Nuclei: The sperm reaches the egg, and the nuclei of both the sperm and egg fuse, creating a diploid zygote.
Zygote Development: The zygote begins to divide by mitosis, forming an embryo, which will implant in the uterus to begin development.
Rr x rr
Using punnet squares:
F1 would be 50% Rr, 50% rr
So F2 would be 50% Rr, 50% rr
Q: Describe the structure of red blood cells and how they are adapted to their function.
A: Red blood cells are biconcave in shape, have no nucleus, and contain hemoglobin. This allows them to efficiently transport oxygen in the form of oxyhemoglobin.