DNA copying passes genetic information from parents to offspring. It also produces small variations during copying, and these variations help populations adapt and survive in changing environments.
Variation may or may not help a particular individual survive. But in a species, variations create diversity, so if the environment changes, some individuals may be better adapted and the species can survive.
In binary fission, one parent cell divides into two daughter cells, as in Amoeba. In multiple fission, one parent cell divides simultaneously into many daughter cells, as in Plasmodium.
Spores are often thick-walled and can survive unfavourable conditions. They are light and easily dispersed by air or water, helping the organism spread to new places and reproduce when conditions become favourable.
Complex organisms have specialised tissues, organs and organ systems. Regeneration can repair or replace some parts, but a small piece usually cannot reorganise itself into all the specialised structures needed for a complete organism.
Vegetative propagation produces plants genetically identical to the parent and preserves desirable traits. It is also useful for plants that do not produce viable seeds, such as banana, orange, rose and jasmine, and it can produce new plants quickly.
DNA contains the information for body design and functioning. Copying DNA ensures that this information is passed to the next generation, while small variations in copying create diversity among offspring.
Pollination is the transfer of pollen grains from the anther to the stigma of a flower. Fertilisation is the fusion of the male gamete from the pollen with the female gamete in the ovule to form a zygote.
The seminal vesicles and prostate gland add fluids to sperm to form semen. These secretions provide nutrition, make transport easier and create a medium in which sperm can move.
At puberty, girls show breast development, growth of hair in the armpits and pubic region, widening of hips, maturation of ovaries, beginning of menstruation and changes in body shape due to sex hormones.
The embryo receives nourishment through the placenta. The placenta provides a large surface where nutrients and oxygen from the mother's blood pass to the embryo, while wastes from the embryo pass back to the mother's blood.
No. Copper-T prevents pregnancy mainly by preventing implantation or fertilisation, but it does not prevent contact with infected body fluids. Barrier methods such as condoms help protect against sexually transmitted diseases.
- a. Amoeba.
- b. Yeast.
- c. Plasmodium.
- d. Leishmania.
Yeast reproduces asexually by budding.
(b) Yeast.
- a. Ovary
- b. Uterus
- c. Vas deferens
- d. Fallopian tube
Vas deferens is part of the male reproductive system.
(c) Vas deferens
- a. sepals.
- b. ovules.
- c. pistil.
- d. pollen grains.
Anthers produce and contain pollen grains.
(d) pollen grains.
Sexual reproduction combines genetic material from two parents and creates more variation among offspring. These variations improve the chances of survival of a species in changing environments and provide raw material for evolution.
The testes produce male gametes, sperm, and secrete the male sex hormone testosterone. Testosterone regulates sperm production and the development of male secondary sexual characters.
Each month the uterus prepares a thick, blood-rich lining for a possible embryo. If fertilisation does not occur, this lining is not needed and breaks down. It is discharged through the vagina as menstrual flow.
A labelled longitudinal section of a flower should show sepals, petals, anther, filament, stigma, style, ovary and ovule. The stamen consists of anther and filament, and the pistil/carpel consists of stigma, style and ovary.
Contraceptive methods include barrier methods such as condoms and diaphragms, hormonal methods such as oral pills, intrauterine devices such as copper-T, surgical methods such as vasectomy and tubectomy, and avoiding sexual intercourse during the fertile period.
Unicellular organisms usually reproduce by simple cell division such as binary fission, multiple fission or budding, because one cell itself is the whole organism. Multicellular organisms have specialised tissues and organs, so they use more complex methods such as vegetative propagation, spore formation, regeneration in simple forms, or sexual reproduction through specialised reproductive organs and gametes.
Reproduction replaces individuals that die and maintains the number of organisms in a population. DNA copying keeps the basic body design of the species stable, while variation helps the population survive environmental changes.
Contraceptive methods are adopted to prevent unwanted pregnancy, plan family size, maintain maternal and child health, and in the case of barrier methods, reduce the risk of sexually transmitted diseases.