IGCSE Biology Reproduction and Inheritance PDF

Reproduction Starter 1.What are the 8 different characteristics of living organisms? 2.Give an example of two of these characteristics.  MAKING SENSE OF IGCSE BIOLOGY Topic 3a (4BI1) Reproduction and Inheritance Reproduction Sexual and A...

Reproduction Starter 1.What are the 8 different characteristics of living organisms? 2.Give an example of two of these characteristics.  MAKING SENSE OF IGCSE BIOLOGY Topic 3a (4BI1) Reproduction and Inheritance Reproduction Sexual and Asexual 3a – Reproduction – Sexual and Asexual Objectives 3.1 Understand the differences between sexual and asexual reproduction. 3.2 Understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo. 3 3a – Reproduction – Sexual and Asexual Two types of reproduction As you know reproduction is one of the 8 characteristics of living things! But there is more than one way of reproducing. ASEXUAL SEXUAL 4 3a – Reproduction – Sexual and Asexual Two types of reproduction - Asexual In asexual reproduction usually cells in one part of the body divide by mitosis (explained later in the course) and then break off from the parent to form a new organism. All the offspring are genetically identical. Asexual reproduction happens in all types of organisms: Fungi Bacteria (E- Animal Plant (Yeast) Coli) (Hydra) (Strawberry) http://commons.wikimedia.org/wiki/User:Diet 5 3a – Reproduction – Sexual and Asexual Two types of reproduction - Sexual In sexual reproduction sex cells called gametes are produced. There are two types, a male gamete and a female. The male gamete must move to the female gamete and fuse with it. This is called fertilisation. The new cell formed is called a zygote. It’s not only animals that do sexual reproduction, flowering plants do as well. 6  3a – Reproduction – Sexual and Asexual Two types of reproduction - Sexual Once you’ve formed this new zygote cell it divides many times by mitosis Egg to form the new organism. Zygot e Sperm Embryo 7 3a – Reproduction – Sexual and Asexual Two types of reproduction - Sexual In humans the male gametes, sperm, are produced in the testes. In the female the ova are produced in the ovaries. The cells inside these organs divide by meiosis (explained later in the course). Meiosis produces cells that are not genetically identical. 8 3a – Reproduction – Sexual and Asexual Two types of reproduction - Sexual Gametes are what we call haploid cells. This means they have half the 23 amount of DNA (23 chromosomes) of a normal cell. This is because they are going to fuse with another gamete to form the zygote which needs the full 23 amount of DNA (46 chromosomes). 9 3a – Reproduction – Sexual and Asexual Two types of reproduction – Sexual or asexual? Humans can only reproduce sexually but in the wider world, many animal and plant species use both types of reproduction, for example: Aphids Strawberries Devil’s Backbone By MedievalRich, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3467494 By Photographer: CrazyD, 26 Octobre 2005 - Own work, CC BY-SA 3.0, 10  3a – Reproduction – Sexual and Asexual Two types of reproduction – Sexual or asexual? Asexual Sexual Produces genetically identical organisms Produces genetically different organisms (clones) Only needs one parent Needs two parents Uses mitosis Uses meiosis to make gamete and then mitosis to grow in size after fertilisation Produces large numbers in short time Slower and produces limited numbers Only source of genetic variation is Offspring show variation mutation 11 3a – Reproduction – Sexual and Asexual CONCEPT CHECK – True or false 1. Asexual reproduction is quick 2. E-Coli reproduce sexually 3. Asexual reproduction uses meiosis 4. Asexual reproduction creates offspring with variation 5. Sexual reproduction can be done with one parent 6. Sexual reproduction uses gametes 7. Gametes are haploid cells 8. The new cell formed in sexual reproduction is a zygote 9. A zygote has 46 chromosomes 10. Some plants can do both sexual and asexual 12 3a – Reproduction – Sexual and Asexual CONCEPT CHECK – True or false 1. Asexual reproduction is quick 2. E-Coli reproduce sexually 3. Asexual reproduction uses meiosis 4. Asexual reproduction creates offspring with variation 5. Sexual reproduction can be done with one parent 6. Sexual reproduction uses gametes 7. Gametes are haploid cells 8. The new cell formed in sexual reproduction is a zygote 9. A zygote has 46 chromosomes 10. Some plants can do both sexual and asexual 13 3a – Reproduction – Sexual and Asexual CONCEPT CHECK – Exam style question Q1: What are the advantages of reproducing asexually (2 Marks) Q2: Suggest why gardeners take cuttings (2 Marks) 14 3a – Reproduction – Sexual and Asexual CONCEPT CHECK – Exam style question Q1: What are the advantages of reproducing asexually (2 Marks) Quick; Only need one parent; Produce large numbers; Q2: Suggest why gardeners take cuttings (2 Marks) To clone plants; Easy/simple; No cost; Parent plant has desirable characteristics; 15