SEXUAL REPRODUCTION IN PLANTS UNIT 4 The reproduction function SEXUAL REPRODUCTION IN PLANTS Natural Science 2. Secondary Education 1

Classifying plants are classified as which can be PLANTS UNIT 4 Classifying plants PLANTS are classified as SEEDLESS PLANTS PLANTS WITH SEEDS which can be GYMNOSPERMS ANGIOSPERMS Click on each box to find out more Natural Science 2. Secondary Education 2

Go back to the Start menu UNIT 4 Classifying plants Seedless plants They do not have flowers, and they produce neither fruits nor seeds. Reproduction occurs through the alternation of generations and they disperse via spores. Two common examples are mosses and ferns. Moss Fern Natural Science 2. Secondary Education Go back to the Start menu 3

Go back to the Start menu UNIT 4 Classifying plants Gymnosperms Their flowers are not particularly attractive and they almost always form structures called cones, often with separate genders. Instead of producing fruit, the female cones mature into developed cones which contain seeds. Some examples of gymnosperms are pine trees, firs and junipers. Female cone Seed Male cone Go back to the Start menu Natural Science 2. Secondary Education 4

Go back to the Start menu UNIT 4 Classifying plants Angiosperms Their flowers are generally attractive. They produce fruit, which contain seeds. There are many different angiosperms, from small grasses to large trees. Seed Flower with androecium (stamen) and gynoecium (pistil) Go back to the Start menu Natural Science 2. Secondary Education 5

Parts of a typical flower UNIT 4 Parts of a typical flower Corrola Petal Stamen Gynoecium or pistil Androecium Sepal Click on androecium and gynoecium to find out more Calyx Natural Science 2. Secondary Education 6

Go back to the Start menu UNIT 4 Parts of a typical flower The androecium It is made up of stamens. Each stamen has: A filament to support the anther. An anther, where pollen grains develop. Male gametes form inside these grains. Anther Pollen grains Go back to the Start menu Filament Natural Science 2. Secondary Education 7

Go back to the Start menu UNIT 4 Parts of a typical flower The gynoecium This is the female reproductive organ. It is shaped like a bottle. It has three parts: Ovary: the widest part, which contains the female gametes. Style: the long part. Stigma: the tip. Stigma Style Ovary Go back to the Start menu Female gamete Natural Science 2. Secondary Education 8

UNIT 4 Fertilisation 2 Pollen grain When the pollen grain reaches the flower’s stigma it forms a pollen tube, which grows along the style until it reaches the ovary. 1 Pollination occurs. Pollen tube 3 Female gamete Male gametes travel down the pollen tube to the ovary and fertilisation takes place. Male gametes Natural Science. Secondary Education, Year 2 9

Seed and fruit formation UNIT 4 Seed and fruit formation The zygote and ovary develop into the seed and fruit The walls of the ovary thicken. The zygote develops into a seed. 2 1 The flower withers and the corolla and the stamen fall away. The zygote begins to develop. 3 The fruit that envelops the seed is formed. Natural Science 2. Secondary Education 10

Seed and fruit formation UNIT 4 Seed and fruit formation Parts of the seed Endosperm: a nutritious substance that feeds the embryo Cotyledons: small leaves that store nutrients. Embryo Hypocotyl Radicle Seedcoat: it envelops and protects the seed. Natural Science 2. Secondary Education 11

Germination Germination 1 2 3 UNIT 4 Germination Germination 1 The buried seed, in proper conditions, begins to absorb water. The embryo starts its development, using the nutrient supplies in the endosperm. 2 The seed coat breaks and a root and stem start to grow, the stem towards the surface and the root away from the surface. 3 When the stem breaks the surface, the cotyledons develop into leaves and begin to carry out photosynthesis. This is how the new plant will get nutrients, which will help it grow and develop. Natural Science 2. Secondary Education 12