Plant Reproduction Year 10

Introduction Biology is the study of …………

Living things have all the characteristics of MRS GREN. M ___________________ R ___________________ S ___________________ G ___________________ R ___________________ E ___________________ N ___________________

Plants differ from animals because … …………………………………………….. All organisms are made of … …………………………………………….. Growth is when an organism increases in size. An organism grows by making new cells in a process called cell division.

Reproduction is when an organism makes more individual organisms.

Asexual reproduction does not involve sex cells (sperms, eggs, pollen). The offspring are genetically identical to the parents. Sexual reproduction involves an egg and a male gamete (sperm or pollen) fusing to form a zygote. The zygote grows into the new individual. The offspring are not identical to the parents.

Cell Division and Reproduction Mitosis is cell division for growth. A plant grows taller and bigger because more cells are being made by mitosis. All cells in a plant have exactly the same number of chromosomes containing the same instructions (genes).

Meiosis is cell division for sex. When a plant reproduces sexually the eggs and the pollen grains (sperms) are made by meiosis. This is a special type of cell division that reduces the number of chromosomes by half. This means that when a sperm fertilises an egg and the nuclei fuse, the new cell (zygote) will have the whole number of chromosomes again.

The zygote will have half its chromosomes from the egg and half from the sperm. A unique individual is produced. This is how sexual reproduction ensures there is variety amongst the offspring. If conditions change at least some of the offspring may have characteristics that enable them to survive and reproduce themselves. This is described as survival of the fittest. It is how evolution occurs.

Flowers and Reproduction Flowers are the sex organs of plants. Most flowers have both male and female parts, but some have them on separate plants so both a male plant and a female plant are necessary to produce fruit e.g. kiwifruit.

Pollination is the transfer of pollen from anthers to stigma. Cross pollination is when the pollen from one flower pollinates another flower on another plant of the same species. Self pollination is when a flower pollinates itself. Cross pollination produces more variation in offspring than self pollination.

Something must cause pollen to go from the anther, where it is made, to the stigma. Many plants use insects but many use wind. Some use animals such as mice or bats.

Insect-pollinated flowers are brightly coloured and smell nice to attract insects. Insects visit to eat the nectar at the base of the petals. As they feed pollen is brushed onto the insect and when it visits another flower some brushes off onto the stigma of this flower. This is pollination. Pollen is spiky and sticky so that it attaches to insects.

Wind pollinated flowers are small and green or brown. They produce huge amounts of tiny, lightweight pollen, which is blown by the wind. Some lands on nearby flowers by chance. They have to produce lots of pollen as much is lost, but they do not have to produce scent or large attractive petals.

Fertilisation is when a male nucleus in the pollen fuses with an egg in the ovary to form a zygote. The zygote grows into an embryo plant which is enclosed in a seed. The ovary develops into a fruit or pod which protects the seeds.

Seed Dispersal Read and complete from Pathfinder Book A, p. 32 Seed dispersal means ………………….. Seeds need to be dispersed away from the parent plant to avoid …………….. for resources. The features that help seeds to be dispersed are called ………………………

Dispersal agent How seeds are dispersed Example Animals Animals eat the seeds which are then passed out in the droppings somewhere else plums Animalsnuts Windsycamore Water Seeds float in water and are carried downstream to a suitable place to live Explosive devices Seed pod may dry and split throwing the seeds out.

TASK Name and draw 3 different seeds. For each one, describe and explain the adaptations it has that help it to be dispersed. “Describe” means to write in words what it looks like. “Explain” means to write how it works to disperse the seeds. Hand in for marking.