3.5 Understand the conditions needed for seed germination

Seeds require:

• Water
• Oxygen
• Warmth

A good way to remeber this is "WOW" (I didn't come up with that, credit to another user, which will remain anonymous.)

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

The pollen tube grows from the stigma, down through the style and into the ovary. This is where fertilisation occurs and it leads to the formation of a seed and/or a fruit. This is quite obviously seen in citrus fruits, such as a lemon, or fruits such as tomatoes (see below)

3.3 Describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination

Figure 1.1 (source: Google Images)

Insect pollinated flowers:

• Large, bright petals to attract insects
• Scented, often with nectar, to attract insects
• Moderate number of pollen grains so they are transferred efficiently by insects
• Sticky or spiky pollen grains, so they stick to insects
• Anthers are located inside the flower (rather than outside) and are firmly attached, so they brush against insects when they try to get the nectar
• The stigma is also inside. It is sticky so pollen grains from insects stick to it when they brush past.

Wind pollinated flowers:

• Small petals with little color - often green or brown
• No scent or nectar because they do not need to appeal to insects
• Large amounts of pollen to increase the chances of it being transferred to another flower
• Anthers are on the outside and filaments are longer so pollen grains are more easily swept away by the wind
• Feathery stigmas form a network outside the flower that helps to catch more pollen from the wind.

3.2 Understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

Fertilisation involves the fusion of a male and female gamete. In mammals, this is the sperm (male) and egg (female). This produces a zygote, which undergoes division by mitosis (so all the cells produced are identical) and eventually develops into an embryo.

At this stage, the cells are unspecialised. They later develop into more specific cells (i.e skin, muscle, brain, blood, etc)

3.1 Understand the differences between sexual and asexual reproduction

Asexual reproduction

• Involves no gametes and only one parent
• Produces genetically identical offspring (clones)
• Commonly happens in plants
• Involves division of cells by mitosis
• Produces more offspring

Sexual reproduction

• Requires two parent organisms
• Produces fewer number of offspring
• Genetic variety in offspring, allows for them to adapt, should the environment change
• Provides offspring a  greater chance of survival in changing conditions
• Involves the fusion of gametes

5.18 Understand how micropropagation can be used to produce commercial quantities of identical plants (clones) with desirable characteristics

Source: https://bam.files.bbci.co.uk/bam/live/content/zh6gd2p/large

• A tissue sample is taken from a 'parent plant'
• It is placed in agar containing appropriate nutrients
• They develop into plantlets
• Transferred to compost where they fully develop

This can be advantageous because:

• It allows a farmer to genetically modify one plant and pass on the modification to many thousands of plants
• Plants grow quicker than they would from the seed
• A (natural) desired trait can be 'copied' into hundreds and thousands of other plants

Its disadvantages are:

• Very small gene pool, which means a disease can wipe out all of the plants at once

5.19 Describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep

The stages are as follows:

1. Remove a donor (diploid) cell with the full genetic information (contained in the nucleus)
2. A cell must be obtained, but one with the capacity to divide. Thus, an egg cell is taken from a sheep.
3. The egg cell nucleus is removed (it is enucleated)
4. Desired DNA is placed into the egg cell. They are fused together with an electric shock. 
5. This newly combined cell divides by mitosis to produce a sheep embryo.
6. The embryo is placed into the womb of another sheep (the surrogate mother)
7. As the cells continue to divide, it will grow into a fetus and eventually be born.

The cloned sheep will have the DNA of the cell donor.

Source: http://media1.shmoop.com/images/biology/biobook_biotechnology_graphik_18.png

5.20 Evaluate the potential for using cloned transgenic animals, for example to produce commercial quantities of human antibodies or organs for transplantation.

As mentioned, one use of cloned, transgenic animals (meaning they have had another organism's DNA inserted into them) is to produce commercial quantities of human antibodies or organs for transplantation. Some examples include:

• Cows with medicine in their milk can be cloned
• Pigs with human hearts can be cloned for organ transplant

Animals can be given genes to produce human antibodies, which can be later injected into humans to help them face infection, rather than allow the immune system to find the appropriate antibody (which would likely take much longer). 

Sheep and cows can be modified to produce human proteins in their milk, which makes it more beneficial for us.

Animals with organs similar enough to human ones can be used for transplants, which would significantly reduce the problem of shortages. However, this may be a problem for ethical reasons (i.e. it can be considered inhumane to breed animals only to cut out their organs)

There are advantages and disadvantages of the process:

😃

• Cloning can happen at any time of year (out of breeding season)
• Infertile animals can be cloned
• Desired traits can be passed on with almost 100% certainty

😓

• Cloned animals may develop problems 
• Cloning is a relatively new technology, meaning that it may have negative consequences that we are not aware of 
• Low success rate (many animals will die horrible deaths)
• Difficult, time-consuming and expensive