Reproduction
Aperçu
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.
Objectifs
- 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.
Carte mentale
Ce theme est schematise pour montrer comment les idees se relient.
Ouvrez la carte mentale dans l'application
Note de cours
Fiche complete disponible sur l'application Green Bridge
Installez l'application Green Bridge CBT sur votre telephone ou votre ordinateur pour acceder a toute la bibliotheque IGCSE : sujets d'examen, baremes, cartes mentales, fiches memo et lecons audio.
Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Reproduction. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- 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
Travaillez ces questions dans l'application
Travaillez ces questions dans l'application
Livres recommandés
Pratiquez des questions blanches
Vous voulez vous entraîner sur des questions blanches sur Reproduction ? Téléchargez lapplication Green Bridge CBT pour accéder à des questions blanches et à des évaluations complètes sur ce sujet.
Téléchargez l'application sur Google Play.
Tout ce dont vous avez besoin pour exceller au JAMB, WAEC et NECO.
