Assessment 1.10Assessed in week 5

Year 11 Biochemistry

Objectives

• By the end of this lesson you need to• 1. Know all the structures of a flower; be able

to label and draw these• 2. Know the function of each of the parts of a

flower• 3. Understand how differences in reproductive

structures of the flower relates to their function and environment

RECAP QUIZ… • What is the female reproductive structure?• What is the male reproductive structure?• List 1 other reproductive structure (not within the

male or female parts)• What is the function of the anther?• Where are the ovules located?• What do the pollen and ovule cells have in common?• What is pollination?• What are two methods in which pollination can occur?• What is the function of petals?

Pollination is..

• the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction.

How does the Pollen travel?• Pollen grains travel from the MALE anther to

the FEMALE stigma via WIND or ANIMAL/ INSECT transportation.

On the LEFT is the STAMEN of a TULIP which is covered in pollen grainsOn the RIGHT is a TULIPDo you think tulip pollen grains would travel by wind or species fertilisation? WHY??!

Wind or species fertilisation?A B C

DE F

Species fertilisation

• Done mostly by birds and insects.• Plants that are fertilised by species usually

have a nectary which contains sweet nectar. The nectary is located at the base but outside the Carpel.

• Petals are the ‘sign’ that a flower has nectar.• Species can feed on this which attracts them

to the flower helping the plant reproduce.

For your assessment..• You need to be able to describe the difference in reproductive

structures of a WIND and INSECT pollinated flower• Then you need to ‘explain how these differences relate to

successful reproduction in flowers• EXAMPLE: Petals in the wind pollinated flower are green and

small. This is because this plant does not need to attract insects to the flower to transfer pollen grains to the stigma of other flowers. Petals in the insect pollinated flower are large and colourful. This attracts insects by signaling that the flower may contain nectar which causes the bee to land on the flower making contact with the anther. Pollen grains stick to the bee and when it lands on the next flower these male sex cells can pollinate and fertilise this flower.

Task: this should take you 30minutes

• Compare and contrast the differences in reproductive structures between wind and animal pollinated flowers.

• ENSURE YOU explain your answers and RELATE IT TO THE SUCCESSFUL REPRODUCTION OF THE FLOWER in terms of its pollination method

• i.e. This flower is pollinated by wind/ insects so this structure is like this so that… resulting in more successful reproduction.

• Key structures you should look at:• Stem, Petals, Nectaries (presence and absence of), Anther,

Filament, Stigma, Style, Pollen

• Stem: stronger, longer, thicker in wind pollinated to hold the anther out to disperse the pollen grains and to hold the stigma high to increase chance of pollen attaching and fertilising the flower. Insect pollinated, it may be brighter to attract insects to increase likelihood of an insect landing on the flower and fertilising the plant, as well as transferring pollen to another flower.

• Petals: small or non existent on wind pollinated flowers as they would cause wind drag and make the plant more likely to get damaged. Plant would have to constantly put energy into repairing structures rather than reproducing. Large and colourful on insect pollinated flowers to attract insects and advertise that the plant may have nectaries of food for the insect. This will to increase likelihood of an insect landing on the flower and fertilising the plant, as well as transferring pollen to another flower.

• Nectaries: present and sweetly scented in many insect pollinated flowers so that the insect in search of food is more likely to land on the flower to obtain food and could transfer pollen to the flower and to other flowers. Often not present, and not scent, on wind pollinated flowers as they do not have to attract insects. Wind pollinated flowers would be wasting energy producing nectar as the wind is not attracted to it therefore this structure has been lost through evolution.

• Anther: the anther in wind pollinated flowers would be exposed and hang outside the flower to ensure wind has maximum access to the pollen grains. This would increase the chances of the pollen grains being transferred to another plant enhancing likelihood of reproduction and species survival. Insect pollinated flowers anthers sit near the nectaries to maximise the chances of pollen being attached to an insect which is feeding on the nectar.

• Filament: the filament supports the anther. In wind pollinated flowers it is strong and long and holds the anther outside the flower so the wind can easily reach the pollen grains on the anther, making it more likely for the pollen grains to be blown to another flower. This increases the likelihood of fertilisation, reproduction and therefore species survival. Insect pollinated flowers filament would not need to be as long or as strong as wind pollinated flowers as the anther is positioned inside the petals, close to the nectaries to make it more likely for insects to make contact with the pollen and carry it to another flower….

• Stigma: the stigma on wind pollinated and insect pollinated flowers are sticky. This enhances the plants ability to pick up pollen grains from the wind and off insects increasing likelihood of fertilisation. Wind pollinated flowers have a comparatively large stigma (compared to an insect pollinated flower) to increase the surface area pollen being carried in the wind has to make contact with.

• Style: the style on wind pollinated flowers is long and strong to hold the stigma within the wind. This allows the stigma to pick up pollen which may be blown around in the wind. The wind can be very strong so the style needs to be strong to support the stigma as without a stigma pollen can reach the ovary and fuse with an ovule to generate offspring. The style on insect pollinated flowers would need to be strong to resist the pressure put on it by insects attempting to access the nectar supply however it does not need to be long and reach outside the flower as the stigma remains inside the flower.

• Pollen: pollen in wind pollinated flowers is present in huge quantities as being transferred by wind is random and the likelihood of pollen being blown to another flower is less than in insect pollinated flowers. This is because once an insect has acquired nectar from a flower it could possibly travel to another flower. Insect pollination is more accurate so these types of plants do not need to generate the extensive quantities of pollen that wind pollinated flowers to. Secondly, pollen of wind pollinated flowers is very light in weight and smooth. This is to give the pollen the best chance of being carried by wind a large distance. Smooth so it doesn’t catch on things and light so that the pollen can be carried in the lightest of winds. Pollen of insect pollinated flowers is sticky, large, rough and produced in smaller quantities. Rough so it sticks to the insect, less because the pollination method is more accurate and large in size and sticky so it is more likely to attach to the insect and be deposited at the next host flower.