3. • Sepal:are leaf like stracture that protect the flower when it is a bud
• Petals: are brightly coloured and scented. Many have a nectary at the base, which makes sugar nectar.Visiting
insects land on the petals to feed on nectar.
• Stamen: are the male sex organs. Each one is made up of two parts the anther(where pollen is made) and the
fillament (a stalk which holds the anther)
• Capels: are the female sex organs. Each capel is made up of a stigma(pollen grains land on the sticky stigma during
pollination)style and ovary(ovule are inside the ovary. Each ovary has a female gamete-egg cell)
Pollination:
is the transfer of pollen grain from the anther to the stigma of the same species. It is complete when the
pollen grains land on the female stigma. The pollen nucleus must now be transfered to the egg cell
inside the ovule, which is inside the ovary.
Ovary-fruit
Ovule -seeds
When pollen garains land on a ripe stigmathey start to grow, forming a
pollen tube which grows down the style to the ovary.the first pollen tube reaches
the ovary. The mlee gamete enters through the micropyle. Fertilisation occurs
when the male gametes fuses with the ovule (female gamete)
4. Feature Insect-pollinated flower Wind- pollinated flower
Petals Present-colorful and sented to
attack insect
Absent or very small and
difficult to see
Nectaries Present-make nectar which is a
sugar liquid food for pollinating
insects.
absent
Stamens Present-usually with short
filament; anthers attached
firmly to filaments;inside the
flower for insects to rub
against.
Present-long filaments
so anther hang ouside
the flower, anthers
looses attach to the
filaments so pollen is
easily blown away
Pollen Small quantity of sticky,spinky
pollen grain that stick easily to
insects body (less number)
More and lighter. Easily
carry out by wind
Carpels Sticky, small, stigmas usually
inside the flowers for insects to
rub against
Large feathery stigma to
catch pollen grains in
the air.
5. Sexual Reproduction in plants
There are two parents that have sex organs which make sex cells or gametes.
In animals -Gametes - male-sperm cells
- female-egg cells
In flowering plants -male gametes are nuclei
. inside pollen grains
- Female gametes are inside stractures called ovules.
Fertalisation: the gamets fuse together.
The fertilised egg or zygote divides to form an embryo
The nuclei in the gametes are called haploid because they contain one set of chromosomes
(23)
a zygote contains two sets of chromosomes (46) known as diploid. Each zygotereceives half its
genes from its male parents and half its genes from its female parents- variation
The offsprings produced are not genetically identical to the parents.
6. Fruits and seeds
After fertilisation:
-zygote becomes the embryo
-the ovule becomes the seed
(develops a testa to protect the embryo)that is made of:
*emryo
*food store
*testa or sead coat
Embryo develops:
-2 cotyledons(seed leaves)
-plumule
-radicle
Loss of water decreases the mass of the seed making it easier to travel a great distance. But chemical reactions occur slowly
Seeds become dormant which means they do not grow any more until some enviromental factor stimulates them
Seeds may remain in this state of dormancy for many years
Dispersal of fruits and seeds
fuction of fruits is to spread the seeds-dispersal by animals or wind.
Helps plants colonise new areas and grow separtely so they do not compete for resources. Important for their survival
Dispersal by wind-fruits and seeds do not weight very much
Animal dispersal
Fleshy fruits brightly coloured to attrack animals
7. Germination:
When the embryo begins to grow. First it appears the radicle from the seed (embryo’s root)
-the radicle emerges first
-the radicle grows down into the soil
-the plumule grows out. It is bent over to protect the tip.
-the radicle contuinues to grow down and the plumule grows up
-the shoot penetrates the soil surface and strightens. The leaves open out and the root make side branches
Conditions:
-Water for seeds to sweel
-oxygen for aerobic respiration-energy
-warm temperature-enzymes work better
Growth:
permanent increase in size and dry mass of an organism, by increasing in cell number or cell size or both.
When cells reach a certain size they divide into two.
In the body this takes place all over the body
In plants it takes place in the root tip and shoot tip, steam and root
Grwoth can be measure by finding the wet mass- water it contains it depends on how much is lost in
transpiration and how much is absorbed
Dry mass: the mass without water. You make water evaporate so then you meassure the real mass of the plant.
tissue and organs develop so that plants and animals become more complex as they grow.increase in
complexity is known as development
