Higher biology Unit 3 P1

Food security

The ability to access food of adequate quality and quantity.

Why is there a higher demand for food now more than ever?

Increase in human population and concerns for food security.

What is sustainable food production?

Food that is produced without degrading natural resources.

5 ways that crop yields can be increased

1. Breeding of higher yielding cultivars

2. Use of fertilisers

3. Protecting crops from pests

4. Protecting crops from diseases

5. Reducing competition by using herbicides

4 characteristics that breeders aim to improve on crops.

1. Nutritional value

2. Resistance to pest and disease

3. Physical characteristics that improve ease of harvesting

4. Characteristics that allow the crops to thrive in particular environmental conditions.

Why do livestock produce less food per unit area?

Livestock loses energy between tropic levels where crops do not.

When is it more suitable to use land for livestock than for crops?

On land that is unsuitable for growing crops.

3 things that can happen when light hits a leaf

Absorbed, reflected or transmitted.

What molecules on a leaf absorb light energy?

Photosynthetic pigments

3 types of pigments

Chlorophyll a - main photosynthetic pigment

chlorophyll b and carotenoids - accessory pigments

What is the light energy used for?

To generate ATP for photolysis.

Role of accessory pigments

Extend range of wavelengths absorbed by plants and pass the energy on to chlorophyll.

Absorption spectra

Absorption spectra graphs show the extent by which different wavelengths of light are absorbed by different pigments in a leaf.

Action spectra

Action spectra graphs show the extent to which wavelengths of light can be used for photosynthesis in a green plant.

How does energy from light lead to the generation of ATP?

Absorbed light energy excites electrons within pigments. Transfer of these electrons through the electron transport chain produces ATP.

What happens during photolysis?

Energy is used to split water molecules into oxygen and hydrogen, oxygen is released and hydrogen reduces NADP to NADPH

What happens during carbon fixation?

Carbon dioxide is fixed by joining with RuBP. 3PG is produced and is phosphorylated by ATP and combined with hydrogen from NADPH to form G3P. G3P is used to generate RuBP and for synthesis of glucose.

Why are reactions of photosynthesis dependant on temperature?

Because they are controlled by enzymes.

Enzyme involved in carbon fixation

RuBisCO

4 uses for the glucose produced in carbon fixation.

1. It can be used as a respiratory substrate

2. Synthesised to starch

3. Synthesised to cellulose

4. Passed to other biosynthetic pathways

What can glucose get converted into through other biosynthetic pathways?

DNA, proteins or fats.

Why are plant field trials carried out?

To compare performance of different cultivars or treatments and to evaluate GM crops.

3 factors that need to be considered when designing plant field trials.

1. Selection of treatments

2. Number of replicates

3. Randomisation of treatments

Why is selection of treatments important when carrying out field trials?

To ensure valid comparisons.

Why must number of replicates be considered?

To take account variability within the sample.

Why must randomisation be considered?

To eliminate bias.

Inbreeding

When selected related plants and animals are bred for several generations until the population breed true to the desired type due to elimination of heterozygotes.

Benefit of inbreeding

Uniformity among offspring and control over characteristics.

Inbreeding depression

Caused by an increase in frequency of individuals who are homozygous for recessive deleterious alleles, these individuals will do less well at surviving to reproduce.

Why are self pollinating plants less susceptible to inbreeding depression?

Deleterious allele combinations are eliminated by natural selection.

How can crossbreeding result in improved characteristics?

May produce a new crossbreed population with improved characteristics.

What must have to happen for the characteristics obtained from crossbreeding to be consistently produced?

Parent breeds must be maintained for offspring to have the desired characteristic.

How can new alleles be introduced?

By crossing with an individual with a different desired genotype.

How are F1 hybrids produced?

Crossing of two different inbred lines.

Benefits of producing F1 hybrids in plants?

Relatively heterozygous crops, increased vigour and yield.

Increased vigour

Increased disease resistance or increased growth rate.

Why are F1 hybrids not usually bred together?

F2 shows too much variation.

How is recombinant DNA technology used to improve breeding programmes?

Able to identify single gene for desirable characteristics and to be inserted into genomes of crop plants.

2 examples of use of recombinant DNA technology.

Insertion of Bt toxin gene, gene for glyphosate resistance.

3 ways plant productivity is reduced

Weeds, pests, diseases

How do weeds reduce plant productivity?

Compete with plants for light, water and nutrients.

How do pests and diseases reduce plant productivity?

Damage the crop which lead to reduced photosynthesis.

What are weeds?

Any plant growing in an area where they are unwanted.

Features of an annual weed

1. Rapid growth

2. Short life cycle

3. High speed output

4. Long term seed viability

Perennial weeds

Weeds that are capable of living for several years.

2 properties perennial weeds with competitive adaptations might have

Storage organs, ability to reproduce using vegetative reproduction (runners, bulbs)

Types of invertebrate pests that affect crops

Nematodes, molluscs, insects

How do nematodes affect crops?

Bore into host plant and live within the plant tissue.

How do molluscs affect crops?

Molluscs such as snails and slugs have rasping mouth parts which can cut through tough plant material.

How do insects affect crops?

Insects like greenfly and caterpillars have piercing or biting mouthparts, which penetrate or chew plant tissue.

What are plant diseases caused by?

Fungi, bacteria and viruses.

How do plants get infected by diseases?

By insects acting vectors.

Cultural methods of weed control

Ploughing, weeding, crop rotation.

Ploughing

Perennial weeds are damaged or buried.

Weeding

Early weeding removes weeds.

Crop rotation

Specific pests die out between plantings of the same crops.

Types of pesticides

Herbicides, fungicides, insecticides, molluscicides, nematicides

Types of herbicides

Selective, systemic

Selective herbicides

Over stimulating the plants metabolism killing the leafy part of the plant.

Systemic herbicide

Absorbed and transported through the vascular system of plants and kill pests that are feeding on the plant.

Potential problems with using insecticides

1. Toxicity to non target species

2. Persistence in the environment

3. Bioaccumulation

4. Biomagnification in food chains

5. Production of resistant pest populations

Bioaccumulation

Build up of a chemical in an organism.

Biomagnification

Increase in concentration of a chemical moving between trophic levels.

Biological control

Control agent is natural predator, parasite or pathogen of the pest.

Example of biological control

Control of glasshouse whitefly with the parasitic wasp Encarsia.

Potential risks of using biological control

Control organism may;

1. Become an invasive species

2. Parasitise other species

3. Prey on other species

4. Become a pathogen of other species.

3 main components of animal welfare

1. Express its natural behavioural patterns

2. Live free from disease

3. Grow vigorously

What is intensive farming?

Keeping many animals in a small space to reduce food. This results in poor animal welfare. It is considered less ethical than free range farming.

Why do farmers choose intensive farming?

Costs are lower so profits can be higher.

What is free range farming?

Animals having more space so they can exhibit their natural behaviours and have a better quality of life. Free range farming is more labour intensive and overall cost is increased.

5 indicators of poor animal welfare

1. Stereotypy

2. Misdirected behaviour

3. Abnormal activity levels

4. Failure of sexual behaviour

5. Failure of parental behaviours.

Stereotypy

When an animal display repetitive actions such as aimless chewing movements in pigs.

Misdirected behaviour

Inappropriate use of normal behaviour such as over grooming of feathers by chickens, leading to feather damage.

Apathy

Used to describe very low levels of activity, examples include animals lying, sitting, or standing in the same position for long lengths of time.

Hysteria

Used to describe very high levels of activity examples include lots of movement or being easily alarmed or panicky.

Failure in sexual behaviour

Failure to seek out a mate.

Failure of parental behaviour

Females may abandon their offspring, act aggressively or even kill and eat them. Some may steal the young of other females.