1.3 - Sexually Reproduction What is Sexual Reproduction?

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Damian Reeves
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1 1.3 - Sexually Reproduction What is Sexual Reproduction? Sexual Reproduction - Genetic information from two cells is combined to produce a new genetically unique organism. Sexual reproduction occurs when two specialized sex cells called gametes (sperm and egg) unite to form a fertilized egg called a zygote. Sex cells from females are called eggs and sex cells from males are called sperm. The union of the sperm cell with the egg cell occurs during mating and is called fertilization. Unit 1 - Life Science 1 / 10

The offspring will have mix traits from both parents, which is important for

2 Notes: Sexual reproduction also occurs in species that we may not think of as having males and females, such as plants and coral. The offspring will have mix traits from both parents, which is important for biological diversity. Both plants and animals can reproduce sexually. Unit 1 - Life Science 2 / 10

3 Meiosis Meiosis is a special type of cell division necessary for sexual reproduction. Summary of Meiosis: The parent cell goes through interphase. There are 2 divisions: 1 st Division: Chromosomes pair up and only one of each pair goes to each daughter cell. = Each cell has only half the number of chromosomes of the parent cell. 2 nd Division: The daughter cells each divide without duplicating their chromosomes. The final result is four daughter cells each with half the number of chromosomes of the parent cell. These cells are gametes. Unit 1 - Life Science 3 / 10

4 Mitosis vs Meiosis Unit 1 - Life Science 4 / 10

5 Sexual Reproduction in Animals Fertilization is the joining of the two gametes. This creates a new single cell (with a full set of chromosomes) known as a zygote. The zygote divides via mitosis, forming a multicellular life form called an embryo. Example: Sexual Reproduction in Humans Unit 1 - Life Science 5 / 10

6 Other points: The development of the embryo may occur inside the female parent (most mammals) or outside, in an egg (most other types of animals). Hermaphrodites are animals that can produce both male and female gametes. They usually mate with members of their own species, but in times of environmental stress, members can fertilize themselves. Examples: garden worms, slugs, and clownfish. Unit 1 - Life Science 6 / 10

7 Sexual Reproduction in Plants Fertilization (male and female gametes join) Zygote Embryo (identical to sexual reproduction in animals) In plants, the reproductive organs are called flowers. Pollen contains male gametes (found on the stamen). Ovules contain the female gametes (found in the pistil). Unit 1 - Life Science 7 / 10

8 Pollination: Occurs when pollen is transferred from the anther of the stamen to the stigma of the pistil. Self-pollination is when pollination occurs within the same plant. Cross-pollination is when the pollen of one plant is carried to the stigma of another by wind, water, or animals (bees, butterflies, etc.). Unit 1 - Life Science 8 / 10

9 Advantages and Disadvantages of Sexual Reproduction Main advantage: Offspring show variation, which helps species survive changes in its environment. Main disadvantage: The embryo must be protected and nurtured during development. Because of this, only a limited number of offspring can be produced. Unit 1 - Life Science 9 / 10

10 1.3 - Review 1 What is meiosis? What is the function of meiosis in sexual reproduction? 2 Compare the processes of mitosis and meiosis (# of chromosomes of the resulting daughter cells, # divisions, and when/where each process is used). Make a diagram to summarize both processes. 3 Explain what a gamete is and how it is formed? Explain what a zygote is and how is it formed? 4 How is sexual reproduction in plants similar to sexual reproduction in animals? 5 If the number of chromosomes in a gamete of an organism is n, is the amount of chromosomes in the body cells of that organism equal to n, n, or 2n? Explain. 1 2 Unit 1 - Life Science 10 / 10

Asexual Reproduction

Asexual Reproduction Only one parent is involved in asexual reproduction. The offspring is genetically identical to the parent. The offspring inherits all of its traits from one parent. Therefore, the