16 1 reproduction in plants and humans

Asexual reproduction is the reproductive process that results in genetically identical offspring from one parent.

Examples of asexual reproduction in living organisms include:

Asexual reproduction can be advantageous because it produces offspring that are genetically identical to their parents, meaning that: In addition to this, asexual reproduction only requires one parent so energy does not need to be expended to find a mate.

Asexual reproduction can be disadvantageous because offspring lack genetic variation, meaning that:

Sexual reproduction is the reproductive process during which the nuclei of two gametes fuse to form a zygote and genetically different offspring are produced.

Fertilisation is the fusion of gamete nuclei.

Gametes are haploid, meaning that they contain half the full number of chromosomes.

True. Zygotes form when two haploid gametes fuse, producing a diploid zygote with the full number of chromosomes.

Sexual reproduction can be advantageous because it generates genetic variation; this means that:

Sexual reproduction can be disadvantageous because offspring are different to their parents, meaning that:

Structures A-D are:

True. Petals of insect-pollinated flowers tend to be brightly coloured to attract pollinator insects.

Anthers produce and release pollen.

X and Y are:

False. Insect pollinated flowers produce large, sticky pollen grains, while wind pollinated flowers produce small, light pollen grains.

Pollination is the process of transferring pollen from the anther to the stigma of a flower.

Fertilisation in plants involves the fusion of a pollen nucleus with an ovule nucleus.

The stigmas of insect pollinated flowers are sticky in order to collect pollen grains from the bodies of visiting insects.

Anthers are adapted in wind-pollinated plants by swinging on long filaments outside the flower to allow the wind to catch pollen grains.

False. Seed germination requires water, oxygen and warmth. This is because the temperature needs to be suitable for enzyme activity.

Self-pollination occurs when pollen is transferred from the anther of a flower to:

Cross-pollination occurs when pollen is transferred from the anther of a flower to the stigma of a flower from another plant of the same species.

True. Self-pollination results in the production of offspring that are less genetically diverse (although they are not clones), meaning that they have a reduced ability to respond to changes in their environment.

Fertilisation in plants involves the following:

The structures are:

The structures are:

The testes are responsible for the production of sperm cells. They also secrete the hormone testosterone, essential for the development of male reproductive organs and secondary sexual characteristics.

True. The prostate gland produces a fluid that contributes to semen volume. This fluid contains enzymes and nutrients that support sperm motility, as well as substances that help neutralise the acidity of the female reproductive tract.

The cervix is a ring of muscle between the vagina and the uterus. It keeps the developing fetus inside the uterus during pregnancy and dilates during birth to allow passage of the baby through the vagina.

The uterus is where the developing embryo implants and develops during pregnancy.

Fertilisation in human reproduction is the fusion of the nuclei of an egg and sperm cell.

The adaptive features of sperm cells include:

Adaptive features of egg cells include:

False. Egg cells are larger and fewer in number than sperm cells, but they are not motile, meaning that they do not move around by themselves.

The embryo is a ball of cells that develops from the zygote.

The structures are:

The function of the placenta is to allow exchange of substances between the mother's blood and that of the fetus. Exchanged substances include:

False. Both pathogens and toxins can cross the placenta.

Secondary sexual characteristics are features that are not present at birth but that develop during puberty.

The two hormones that control the development of secondary sexual characteristics are:

Examples of secondary sexual characteristics that develop in females include:

Examples of secondary sexual characteristics that develop in males include:

The menstrual cycle is the sequence of events that includes the thickening of the uterus lining, ovulation and menstruation; it is controlled by a series of hormones.

Ovulation is the release of an egg cell from the ovaries during the menstrual cycle.

Oestrogen and progesterone are secreted from the ovaries. Specifically, oestrogen is secreted by the developing follicle and progesterone by the empty follicle, known as the corpus luteum.

FSH causes an egg to start maturing in the ovary. It also stimulates the ovaries to start releasing oestrogen.

False. LH causes ovulation to occur. It is FSH that causes an egg cell to begin to mature.

Oestrogen causes the uterus lining to thicken during the first part of the menstrual cycle. It also interacts with other hormones to bring about maturation of an egg cell.

False. A decrease in progesterone levels at the end of the cycle results in the loss of the lining during menstruation.

A sexually transmitted infection is an infection that is transmitted through sexual contact.

HIV is a pathogen that causes an STI. HIV stands for human immunodeficiency virus.

False. HIV is a pathogen and infection with HIV can lead to the disease AIDS.

HIV is transmitted via body fluids, e.g. during sexual intercourse, contaminated blood, sharing needles, or across the placenta.

The spread of STIs can be controlled by: