3.1-3.7 sexual/asexual reproduction, reproduction of plants

Advantages of sexual reproduction

• produces variation - if the environment changes it is likely that an organism in the species will have a characteristic that allows them to survive (survival advantage), prevents extinction

• Allows selective breeding- can breed organisms desirable characteristics to breed offspring with more desirable characteristics, speeds up natural selection

Advantages of asexual reproduction

• only one parent is needed

• Faster than sexual reproduction

• Lots of identical offspring can be produced

Disadvantages of sexual reproduction

• high energy and time

• Slower process

• Requires two parents

Disadvantages of asexual reproduction

• Lack of genetic variation - entire population susceptible to a single disease/environmental shift

• Limited adaptability - hindered evolution

Differences between sexual and asexual reproduction

S- two parents, A- one parent

S- involves gametes (sperm, egg), A- no gametes involved

S- requires fertilisation, A- none

S- offspring are genetically varied, A- offspring are genetically identical

S- involves meiosis and mitosis, A- primarily involves mitosis

S- slower and more energy, A- faster and less energy

What does fertilisation involve

The fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

A name and adaptation

Petals- large and bright to attract insects

B name and adaptation

Anther- produces and holds pollen, stiff and attached inside the flower so that insects can brush past

What are B and D (C) and function?

Stamen - male reproductive organ

D name and function

Filament- elevates and supports the anther

E name and adaptation

Stigma- inside flower, sticky so pollen grains stick to it when insects brush past

F name

Ovary

G name

Ovule

H name and adaptation

Nectary- secretes nectar which is scented to attract insects

I name

Sepal

Different types of plants

Insect pollinated and wind pollinated

A name

Anther

B name

Filament

C name

Stigma

How are wind pollinated petals adapted

Small and dull, do not need to attract

How are wind pollinated plants’ nectar adapted?

There is no nectar or scent, do not need to attract

How are wind pollinated plants’ pollen grains adapted

Smooth and light so they can be easily carried in the wind and in large amounts to make sure some reach other flowers

How are wind pollinated plants’ anthers and filaments adapted

They are outside the flower, loose on long ligaments so that pollen can be easily released

How are wind pollinated plants’ stigma adapted

They are outside the flower, feathery so it is easier to catch pollen grains drifting in the wind

What are the sex cells in plants that reproduce sexually?

Pollen grains are the male gametes, ovule is the female gamete

Describe the process of seed and fruit formation

1. Pollen grains land on stigma (via insect or wind pollination)

2. Pollen tube grows out of the pollen grain and down the style

3. The male nucleus travels down the pollen tube from the pollen grain to fuse with the female egg nucleus in the ovule, forming a zygote

4. The zygote undergoes mitosis to form a seed

5. The ovule will become the seed and the ovule wall will become the seed coat

6. The ovary will become the fruit of the plant

What is germination

The process in which seeds begin to develop into a new young plant

What conditions are needed for seed germination and why?

Water- needed to activate enzymes to break down the starch food reserves in the seeds

Oxygen- needed fr aerobic respiration to release energy for growth

Warmth- optimum temperature for enzymes will increase growth

What practical can you do to investigate the conditions needed for seed germination?

1. Set up 4 boiling tubes with 10 cress seeds in each, sitting on cotton wool

2. Tube A should have dry cotton wool and kept at 20°C

3. Tube B should have moist cotton wool and kept at 20°C

4. Tube C should have boiled water that has been cooled, covered with a layer of oil and kept at 20°C

5. Tube D should have moist cotton wool but kept at lower temp eg 4°C

Results: only Tube B seeds will germinate because it has water, temp, oxygen.

What is an embryo (in a plant)

Young root and shoot that becomes the adult plant

What is a food store

Starch for the plant to use until it is able to carry out photosynthesis

What is a seed coat

A protective covering

What is an example of natural asexual reproduction of plants?

Runners - grow horizontally over soil surface and put down roots to form new plants

Eg. Strawberry plants

What is an example of artificial asexual reproduction of plants

Cuttings- a piece of a parent plant that’s cut off and placed in a growth medium to grow into a new identical plant