CORE Biology (Short Course) - 9221 OxfordAQA

Reproduction

Gbogbo ọrọ náà

Pull a strawberry plant out of a bed in late summer and you will find it trailing a thin horizontal stem across the soil, with a small rooted plant at the far end. That little plant had no other parent. Every gene it carries came from the plant you are holding. A few metres away, a bee is carrying pollen between two flowers, and the seed that results from that visit will carry instructions from two different individuals. Both events are reproduction, and the difference between them shapes almost everything that follows in genetics.

This lesson takes the two forms apart. You will see what a gamete is and what actually happens when two of them fuse, why that fusion produces offspring that resemble their parents without copying either of them, and why reproduction from a single parent gives you offspring so alike that biologists call them clones. Then you will weigh the two against each other the way an examiner does: not asking which is better, but asking which one wins in a particular field, on a particular farm, in a particular changing climate.

Ebumnobi

There are two forms of reproduction: sexual reproduction - the joining (fusion) of male and female gametes. The mixture of the genetic information from two parents leads to variety in the offspring; asexual reproduction - no fusion of gametes and only one individual is needed as the parent. There is no mixing of genetic information and so no genetic variation in the offspring. These genetically identical individuals are known as clones.

Maapụ uche

E seela isiokwu a ka ị hụ otu echiche si ejikọta.

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Akwụkwọ Ọmụmụ

Every species alive today descends from ancestors that managed to make more of themselves. There are only two ways of doing it. In one, two parents each contribute a special sex cell, the two cells join, and the offspring carries a blend of instructions that has never existed before. In the other, one parent divides, buds, sprouts or sheds a fragment, and the offspring carries a faithful copy of that single parent's instructions. Biology calls the first sexual reproduction and the second asexual reproduction, and the whole of this topic sits in the gap between them.

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Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Reproduction. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Which statement about asexual reproduction is correct? A. Two parents are needed B. Male and female gametes fuse C. The offspring are genetically identical to the parent D. The offspring show a wide range of genetic variation Answer: C
A human body cell contains 46 chromosomes. How many chromosomes are in a human sperm cell? A. 11 B. 23 C. 46 D. 92 Answer: B
What is a clone? A. A cell formed when two gametes fuse B. A group of genetically identical individuals produced from one parent C. A sex cell with a single set of chromosomes D. An offspring produced from two parents of different varieties Answer: B
Which of these is produced by sexual reproduction? A. A potato plant grown from a tuber B. A strawberry plant at the end of a runner C. A seedling grown from a seed D. A new Hydra formed as a bud on the side of a parent Answer: C
Why can a population of genetically identical plants be destroyed completely by a new disease? A. The plants are always grown close together B. The plants have no way of reproducing C. No individual differs from the others, so none is likely to be resistant D. Cloned plants grow more slowly than plants grown from seed Answer: C

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