Sexual Reproduction in AngiospermsAdministrator2020-10-06T12:48:31+02:00
Seeds are produced in flowers, which are the sexual organs of Angiosperms.
The components of a flower usually include:
male structures called stamens for producing pollen (containing male sex cells)
female structures called stigma (for receiving pollen), style and ovary (for producing female sex cells)
petals (for attracting pollinators)
sepals (for protecting the flower bud)
Pollination and fertilisation are essential processes for flowers to produce seeds.
Pollination is the transfer of pollen between plants of the same species for the purpose of fertilisation.
Wind and water can facilitate pollination.
Pollination can also be aided by pollinators such as insects, birds, mammals, etc.
Flowers have special adaptations to promote pollination, such as large colourful petals, scent and sweet nectar to attract insects and birds.
Pollinators play an important role in the production of food crops (such as maize) for humans.
Fertilisation is the fusion of the male and female sex cells to produce seeds
During fertilization the following happens: each mature pollen grain contains two male sex cells. When the pollen attaches to the stigma of a flower from the same species, the pollen produces a pollen tube, which grows down the neck of the:
style, transporting the male sex cells to the ovule. Within the embryo sac of the ovule, one male sex cell fertilizes the egg, which develops into a seed.
The other male sex cell unites with two cells in the embryo sac and this results in the development of the:
endosperm, the starchy food that feeds the developing seed.
The ovary enlarges and becomes a fruit.
The seeds are contained in fruit .
Fruits and seeds are dispersed in various ways.
Teacher Input 1
Greet the learners.
Ask them if they can remember what flowering plants are called.
What else can they remember about Angiosperms? You can refer back to Presentation 5, which included the following facts:
it is the most diverse of plant groups.
it is the largest group in the plant kingdom.
all angiosperms use flowers for reproduction.
seeds grow inside the flower after fertilisation.
Tell learners that they are going to learn how these flowering plants reproduce.
Show and explain PRESENTATION 1:Sexual Reproduction.
Learner Activity 1
Prepare for this activity by either collecting large flowers like hibiscus flowers or ask the learners to bring a flower.
Ideally have one flower between 2 learners. Each group must have a scalpel joined to a scalpel handle. If these are unavailable, use small, sharp knives.
The learners will need to follow the instructions in WORKSHEET A very carefully, especially if they are using the scalpels as they are very sharp.
Note that there is no memorandum for this worksheet. Learners’ sketches are to be compared with the sample sketch in the worksheet.