3.4

objective 3.4: understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation



1. the male nucleus travels down the pollen tube to the ovulw
2. the male nucleus will fertilise the ovule
3. this leads to the formation of the zygote which in turn leads to the growth of the embrionic plant
4. outside of the ovule the seed coat forms
5. another name for seed coat is testa
6.inside, in addition to the zygote, the cotyledon forms
7. the cotyledon is a food store used for the plant before the leaves can provide energy
8. the walls of the ovary thicken by adding sugar and protein.
9. fruit is the wall of ovary/carpel 

3.3b

objective 3.3b: describe the structures of an insect pollinated and a wind pollinated flower and explain how each is adapted for pollination.



wind pollination= transfer of pollen grain from anther of one plant to stigma of the other through the air carried by the wind

the adaptations a wind pollinated plant would have would be:
lightweight pollen grain, maybe with wings so to catch the wind better.

the anther will hang well clear of the main flower structure so they are exposed to the wind.

the stigma will have a large surface area maybe in a feather-like structure to catch the pollen grains as they pass through the air. the stigma will also be well clear of the main flower structure and be exposted.

grass is an example of a wind pollinated plant

grass has no colour, scent, or nectaries as there is no need to attract insects as it is wind pollinated. the features if an insect pollinated plant would be a waste of energy.

3.3a

3.3a: describe the structures of an insect pollinated and a wind pollinated flower and explain how each is adapted for pollination.



in pollination there must be a transfer of pollen from the anther of one plant to the stigma of another.
when pollination occurs between 2 separate plants it is called cross pollination.

pollen is a small structure which contains the male nuclei

the transfer of pollen in an insect pollinated plant is by insects. the flowers must attract insects.
adaptions of plant to attract insects include;
signals. - the colourful petals, scents
value/reward- food (from nectaries produce fructose), pollen as protein

the male part of the flower= stamen composed of anther and filament
the female part of flower= carpel composed of stigma, style, ovary (which contains eggs called ovules)

2.81

objective 2.81 : describe posotive phototropism of stems




phototropism= growth in responce to light

posotive phototropism= growth towards light

if a stem's tip is exposed to uniform light (light from all directions) the stem will grow upwards

if the light source is from the side the tip will grow towards the light
this is an exaple of posotive phototropism of the stem

light on one side causes the hormone AUXIN on the other side to grow sideways towards the light. this is how the stem grows sideways.

2.80

objective 2.80 : describe the geotropic responses of roots and stems.





Geotropic=growth in response to gravity

growth downwards= posotive geotropism
growth upwards= negative geotropism

stems/shoots grow up, therefore they have negative geotropism
roots grow down, therefore they have posotive geotropism

2.79

Objective 2.79: understand that plants respond to stimuli

Stimuli is changes in the environment, examples are temperature and light changes.
Plants have receptors to detect stimuli and respond
the  responce is growth.
growth in responce to stimuli is called TROPISM
trpism in responce to:
gravity; geotropism
light; phototropism

the connection between the receptor and the responce usually takes the form of plant hormones, often known as plant growth regulators
an example of this would be AUXIN