What is sexual reproduction?
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What is sexual reproduction?
Sexual reproduction involves the fusion of the nuclei of two gametes to form a zygote, producing offspring that are genetically different from each other.
What is a gamete?
A gamete is a sex cell (e.g., sperm and ovum in animals; pollen nucleus and ovum in plants) that contains half the number of chromosomes as a normal body cell.
What is asexual reproduction?
Asexual reproduction involves only one parent, with no gametes or fertilisation, resulting in offspring that are genetically identical to the parent (clones).
What is binary fission?
Binary fission is a type of asexual reproduction in bacteria where the organism produces exact genetic copies of itself.
How do sexual and asexual reproduction differ in the number of parents involved?
Sexual reproduction involves two parents, while asexual reproduction involves only one parent.
What type of cell division is involved in sexual reproduction?
Sexual reproduction involves meiosis, which produces genetically diverse gametes.
What type of cell division is involved in asexual reproduction?
Asexual reproduction involves mitosis, resulting in genetically identical offspring.
What is fertilisation?
Fertilisation is the fusion of gametes.
What is the role of meiosis in sexual reproduction?
The role of meiosis in sexual reproduction is to break up parental combinations of alleles.
True or False?
The fusion of gametes produces new combinations of alleles.
True.
The fusion of gametes produces new combinations of alleles. New alleles are formed because each parent contributes their alleles to form a new diploid cell.
What are the male and female gametes in animals?
Male gametes are sperm cells, and female gametes are ova (eggs).
What are the male and female gametes in plants?
Male plant gametes are carried in pollen grains, and female plant gametes are held in the ovules within the ovary.
What happens during fertilisation?
Fertilisation is the fusion of a male and female gamete, producing a zygote with new combinations of alleles, leading to genetic variation.
How do male and female gametes differ in reproductive strategies?
Males produce many thousands of sperm per ejaculation to increase chances of fertilisation, while females typically release only one egg per menstrual cycle.
Why is the male gamete smaller than the female gamete?
The male gamete is smaller than the female gamete because the male gamete travels to the female gamete, with less food reserves than the egg.
What is the function of the ovaries?
The ovaries produce ova (eggs) and female sex hormones like estrogen and progesterone.
What is the function of the fallopian tubes (oviducts)?
The fallopian tubes transport the egg from the ovary to the uterus and are the site where fertilisation typically occurs.
What is the function of the uterus?
The uterus is where a fertilised egg implants and develops into a fetus.
What is the function of the cervix?
The cervix is the lower part of the uterus that opens into the vagina; it allows the passage of sperm into the uterus and, during childbirth, dilates to allow the baby to pass through.
What is the function of the testes?
The testes produce sperm cells and male sex hormones like testosterone.
What is the function of the sperm duct?
The sperm duct transports sperm from the testes to the urethra during ejaculation.
What is the function of the prostate gland?
The prostate gland produces a fluid called semen, which contains nutrients required for the sperm cells to swim.
What is the urethra?
The urethra is a tube that transports urine from the bladder out of the body. Both males and females have a urethra.
What is the menstrual cycle?
The menstrual cycle consists of the ovarian and uterine cycles. It is the sequence of events that includes the thickening of the uterus lining, ovulation and menstruation; it is controlled by a series of hormones.
What is the role of oestradiol (oestrogen) in the menstrual cycle?
Oestradiol causes the uterus lining to thicken during the first part of the menstrual cycle. It also interacts with other hormones to bring about the maturation of an egg cell.
What happens to oestradiol levels during the menstrual cycle?
Oestradiol levels rise from day 1 and peak just before day 14. The peak in oestradiol occurs just before the egg cell is released.
True or False?
An increase in progesterone results in the loss of the uterus lining.
False.
A decrease in progesterone levels at the end of the cycle results in the loss of the lining during menstruation.
What happens to progesterone levels during the menstrual cycle?
Progesterone levels are low from day 1 – 14 and starts to rise once ovulation has occurred. Levels then decrease towards the end of the cycle.
What is the role of FSH (follicle-stimulating hormone) in the menstrual cycle?
FSH is released by the pituitary gland and causes an egg to start maturing in the ovary. It also stimulates the ovaries to start releasing oestrogen.
What hormone is released by the pituitary gland when oestrogen levels peak?
When oestrogen levels reach their peak the pituitary gland is stimulated to release LH (luteinising hormone).
Which hormones interact in a negative feedback loop within the menstrual cycle?
Oestrogen and FSH interact in a negative feedback loop. When oestrogen levels are high enough, it inhibits the secretion of FSH.
OR
Progesterone, FHS and LH interact in a negative feedback loop. Progesterone thickens and maintains the endometrium but also inhibits the secretion of FSH and LH from the pituitary gland.
Which two hormones interact in a positive feedback loop during the menstrual cycle?
Oestrogen and LH interact in a positive feedback loop. After ovulation, LH causes the wall of the follicle to develop into the corpus luteum, which secretes more oestrogen.
Which hormones are used during IVF (in vitro fertilisation) treatment?
The hormones FSH, LH and progesterone are given during IVF.
FSH and LH stimulate the development of follicles
Progesterone is given to ensure the endometrium is maintained
What is superovulation?
Superovulation is when many more follicles than normal begin to mature due to artificial doses of FSH given at a much higher concentration than is present during a normal menstrual cycle.
Define fertilisation.
Fertilisation is the fusion of gamete (haploid) nuclei, resulting in the formation of a zygote (diploid nucleus).
What is the process of fertilisation in humans?
Fertilisation in humans involves the fusion of a sperm cell with an egg cell, and entry to the egg by the sperm nucleus which has its tail and mitochondria destroyed in the process.
What is the result of fertilisation?
The result of fertilisation is the formation of a zygote/fertilised egg cell.
What is a zygote?
A zygote is a diploid cell formed by the fusion of a sperm and an egg cell during fertilisation.
What is the function of the sperm's enzymes when reaching the egg?
The sperm's enzymes digest the egg cell's glycoprotein layer to allow the sperm to reach the egg's membrane.
True or False?
Vesicles released from the egg destroy the sperm's nucleus upon entry.
False.
Vesicles released from the egg destroy the sperm's flagellum (tail) and mitochondria upon entry.
True or False?
The sperm's mitochondrial DNA is inherited by the zygote.
False.
The sperm's mitochondrial DNA is destroyed, so it is not inherited by the zygote.
True or False.
The nuclear membranes of both sperm and egg dissolve during the process of fertilisation.
True.
During fertilisation dissolution of nuclear membranes of both sperm and egg nuclei occurs.
What happens after the nuclear membranes of the sperm and egg nuclei dissolve?
After the nuclear membranes dissolve, all condensed chromosomes participate in joint mitosis to produce two diploid nuclei.
What is the purpose of joint mitosis in the final stages of fertilisation?
The purpose of joint mitosis is to produce two diploid nuclei which become the zygote.
What are the main stages of sexual reproduction in flowering plants?
The main stages of sexual reproduction are the production of gametes inside ovules and pollen grains, pollination, pollen development and fertilisation to produce an embryo.
True or False?
Pollen grains contain male gametes.
True.
Pollen grains contain male gametes.
State the function of the anther.
The anther is the part of the stamen that produces the male gametes.
What happens after fertilisation in flowering plants?
After fertilisation, the ovule becomes a seed (an embryo) and the ovary develops into the fruit.
What is the stigma on a flower?
The stigma is the part of the female reproductive organ that receives the pollen.
What is the function of the ovary in a flower?
The ovary contains the ovules where female gametes develop.
What is the role of the pollen tube in fertilisation in plants?
The pollen tube grows from the pollen grain down the style to the ovary, allowing male nuclei to travel to the ovule.
True or False?
Some flowering plants are hermaphroditic which means they contain both male and female parts.
True.
Some flowering plants are hermaphroditic which means they contain both male and female parts. However, reproduction in flowering plants is sexual, even if a plant species is hermaphroditic.
Define cross-pollination.
Cross-pollination occurs when pollen from one plant is transferred to the stigma of another plant of the same species.
True or False?
Cross-pollination increases genetic variation.
True.
Cross-pollination increases genetic variation.
What is self-pollination?
Self-pollination occurs when pollen from a flower lands on its own stigma or on the stigma of another flower on the same plant.
State the function of nectar in insect-pollinated flowers.
Nectar attracts insects to the flower, aiding in the transfer of pollen.
True or False?
Pollen from insect-pollinated flowers is sticky.
True.
Pollen from insect-pollinated flowers is sticky to adhere to insects.
What adaptation do wind-pollinated plants have to aid in pollination?
Wind-pollinated plants produce large amounts of light, non-sticky pollen that can be carried by the wind.
Define self-incompatibility mechanism.
A self-incompatibility mechanism is a genetic process that prevents self-pollination by inhibiting pollen tube growth or fertilisation from the same plant.
What are adaptations of plants to prevent self-pollination ?
Adaptations to prevent self-pollination, and promote cross-pollination include different maturation times for pollen and stigma, separate male and female flowers or male and female plants.
True or False?
Wind-pollinated plants are less likely to self-pollinate than insect-pollinated plants.
True.
Wind-pollinated plants are less likely to self-pollinate due to the random dispersal of pollen by the wind.
What is a disadvantage of self-pollination?
A disadvantage of self-pollination is that it reduces genetic variety in the offspring, leading to inbreeding and less adaptability to environmental changes.
Define seed dispersal.
Seed dispersal is the process of distributing seeds away from the parent plant to reduce competition.
True or False?
Pollination and seed dispersal are the same process.
False.
Pollination is the transfer of pollen from anther to stigma, while seed dispersal is the distribution of mature seeds.
What are the methods of seed dispersal?
Methods of seed dispersal include wind, water, animals, and explosions.
State the role of animals in seed dispersal.
Animals help in seed dispersal by eating fleshy fruits and dispersing seeds through egestion or by carrying sticky seeds on their fur.
Define germination.
Germination is the start of growth in a seed after dormancy when conditions become favourable.
True or False?
Water is required for seed germination.
True.
Water is required for seed germination to allow the seed to swell, burst the seed coat, and activate enzymes.
What is the function of the radicle during germination?
The radicle is the first structure to emerge from the seed and forms the initial root that grows downward into the soil.
What are the three factors required for successful germination?
The three factors required for germination are water, oxygen, and warmth.
What is the role of the hypocotyl in seed germination?
The hypocotyl is the curved portion of the plant shoot that appears above ground and grows upwards, helping the seedling to emerge.
What is the function of food reserves during germination?
Food reserves provide energy and nutrients for the growth and development of the embryo during germination.
What are cotyledons?
Cotyledons are early leaf structures in a seed that help transfer food reserves to the embryo during germination.
Describe the mobilisation of food reserves during germination.
During germination, food reserves in the seed, mainly endosperm, are mobilised and transferred to the growing embryo to support its development.