IGCSE Biology Unit 8: Plant Reproduction

Plant Reproduction

• Reproduction is the production of an offspring, involving the passing of genetic information from parent to offspring.
• There are two types of reproduction: asexual and sexual.

Asexual Reproduction

• Asexual reproduction involves the production of offspring from one parent.
• Methods of asexual reproduction include:
• Binary fission
• Spore formation
• Budding

Binary Fission

• Binary fission occurs in plant cells and involves the production of two identical daughter cells.
• The process involves:
• DNA replication
• Cell division
• The formation of two identical daughter cells
• Binary fission has two important roles:
• It allows for growth and repair in multicellular organisms.
• It enables unicellular organisms to produce offspring.

Spore Formation in Fungi

• Spore formation occurs in fungi and involves the production of microscopic reproductive structures called spores.
• Spores are formed in sporangia and are released when the sporangium matures.
• Spores can develop into new fungi if they land in favorable conditions.

Budding in Yeast Cells

• Budding is a method of asexual reproduction that occurs in yeast cells.
• The process involves:
• The formation of a bud on the surface of the yeast cell.
• The nucleus of the cell divides into two.
• One of the nuclei moves into the bud.
• The bud separates and continues to grow.

Sexual Reproduction

• Sexual reproduction involves the production of offspring from two parents.
• The process involves:
• The production of gametes (sex cells) by the parents.
• The transfer of the male gamete to the female reproductive organ.
• Fertilization, which occurs when the gametes fuse to produce a zygote.
• The offspring produced by sexual reproduction are genetically different from their parents and exhibit genetic diversity.

Pollination

• Pollination is the transfer of pollen from the anther to the stigma of a flower.
• There are two main types of pollination:
• Insect pollination, which occurs when pollen is transferred by insects such as bees, butterflies, and ants.
• Wind pollination, which occurs when pollen is transferred by wind.

Insect Pollination

• Insect-pollinated flowers have adaptations that attract insects, such as:
• Large, colorful petals.
• Nectar production.
• The stigma is hooked or located inside the flower, surrounded by the anther and petals.

Wind Pollination

• Wind-pollinated flowers have adaptations that allow for the transfer of pollen by wind, such as:
• Small, inconspicuous flowers.
• No nectar production.
• The stigma is sticky and feathery, acting as a net to trap pollen grains.
• The pollen is produced in large numbers and is very light.

Fertilization

• Fertilization occurs when a pollen grain reaches a stigma and a pollen tube grows down the style.
• The process involves:
• The pollen tube reaching an ovule.
• The male gamete moving down the pollen tube.
• The male nucleus fusing with the female nucleus to form a zygote.
• The zygote dividing many times to produce an embryo.

Seed and Fruit Formation

• Once the ovules are fertilized, the ovary develops into a fruit, and the ovules develop into seeds.
• The seed is made up of:
• An embryo, which consists of a young shoot and a young root.
• One or two cotyledons, which are food stores.
• A seed coat, which is the thickened outer wall of the ovule.
• A micropyle, which is a small hole that marks the point where the pollen tube entered the ovule.

Seed Dispersal

• The main function of fruit is seed dispersal, which allows plants to establish themselves in new habitats.
• Methods of seed dispersal include:
• Parachute fruits and winged fruits, which have feathery hairs or wing-like structures that allow them to float over long distances.
• Explosive fruits, which release seeds when the fruit splits open.