Mocks - remembered

Functions and adaptations of the waxy cuticle

Reduces water loss from the leaf, is transparent to allow light to pass through, prevents the entry of pathogens into the leaf

Functions of the upper epidermis

Thin and transparent to allow light to pass through to the palisade mesophyll layer below

What happens at the stomata

GAS EXCHANGE. Also evaporation of water - this is not actually wanted, but occurs as the plant needs carbon dioxide to diffuse in for photosynthesis.

Vascular bundle diagram

Xylem on the inside; phloem on the outside

Transpiration

The EVAPORATION of water from the stomata on the surface of the leaf

Differences between xylem and phloem

• Xylem - dead cells; phloem - living

• Xylem - thick cell wall (no end wall between cells) stiffened with lignin; phloem - thin, cellulose cell wall

• Xylem - impermeable; phloem - permeable

• Xylem - direction of travel is up ONLY; phloem - direction of travel is both up and down

• Xylem - transports water and mineral ions from the roots to other parts of the plant; phloem - transports sucrose and amino acids

Adaptations of root hair cells

• High surface area to volume ratio for osmosis - root hairs increase surface area

• Mitochondria, so aerobic respiration can occur, to release ATP energy for active transport

• Vacuole to help control water potential and to store cell sap (containing starch, which can be broken down into glucose for respiration)

• Partially permeable membrane for osmosis

• Ribosomes to make carrier proteins for active transport

How does water enter the roots (and after, where does it go and why)

Minerals (e.g. nitrates) are actively transported into the root hair cells. This lowers the water potential into the cells, so water moves in, from a higher to lower water potential, by osmosis. It enters the xylem from the roots, and moves upwards, against gravity, to the leaves, as transpiration is occurring, and water molecules are pulled up to replace those lost, as water is cohesive.The water vapour then exits the leaf through the stomata.

Fertilisation process in a plant

• A pollen grain lands on the stigma, and if from the same species, germinates on the stigma

• A pollen tube grows down the style, by releasing digestive enzymes pacman

• The pollen tube reaches the ovary, and enters the ovule through the micropyle

• Fertilisation occurs: the fusion of the male gamete (pollen grain nucleus) and the egg

• The ovary becomes a fruit, the ovules become seeds, and the ova become embryos (part of the seed)

4 conditions needed for germination

Light, warmth, water, oxygen

Why is light needed for germination

To activate plant growth regulators

Why is water needed for germination

It enters the seed through the micropyle, and activates enzymes, particularly amylase to digest starch into maltose, and maltase to digest maltose into glucose

Process of micropropagation

• Use a scalpel to remove explants from the original plant

• Wash in bleach to sterilise the explants

• Transfer the explants, under aseptic conditions, onto agar jelly and leave them to grow in a well-lit area

• The agar jelly is a plant growth medium that contains sucrose, to provide glucose, for respiration; nitrates, to form amino acids; phosphates, to form nucleotides and ATP; magnesium, to form chlorophyll; and plant growth hormones

• The explants will grow into plants that are genetically identical to the parent plant

Advantages of micropropagation

• You can do it at any time of the year

• Produces large quantities of plants

• Plants are all genetically identical so desired qualities can be replicated

• Quicker than sexual reproduction

• Disease-free plants

• Uniform quality and ripening time

Disadvantages of micropropagation

• No genetic variation so the population of plants is more vulnerable to disease

• Expensive procedure

• Can only be carried out by trained individuals

Where are the different digestive enzymes produced?

• The pancreas produces amylase, trypsin and lipase

• Amylase is also produced by the salivary glands

• Pepsin is produced by the stomach walls

• Peptidase and maltase are produced by the walls of the small intestine (duodenum)

Test for lipids

Emulsion test: add 2cm3 of ethanol to the food sample in a test tube, seal it with a bung, and shake vigorously. Allow the contents to settle, then pour the contents of the test tube into another test tube half filled with water. If the water turns from clear to cloudy, lipid is present.

Humus

A dark, organic material that forms in soil when plant and animal matter decays

Impacts of deforestation

• Soil erosion: water is no longer intercepted by the canopy, and roots no longer hold soil in place. Loss of leaves means less humus in the soil. Wind and rain remove top soil.

• Atmospheric carbon dioxide increases, as carbon stored in tree trunks is transferred into the air by burning or decay. There is also less photosynthesis occurring.

• There is disturbance of the water cycle, as there is less transpiration, so rain clouds don’t form, so the local area becomes drier.

• There is mineral leaching into rivers, which leads to eutrophication, as minerals are no longer absorbed by roots of trees.

• There is a loss of medicinal plants.

Benefits of fish farming

• Reduces overfishing, which leads to significant declines in wild fish populations

• Large numbers of fish produced

• Can selectively breed fish to ensure high-quality, fast-growing fish

• Can protect fish against predators

• Can control water quality (so fish do not consume pollutants)

• Can control feeding to ensure rapid growth

What nutrients for humans are there in fish

Proteins

How do fish farms ensure high yield

• Water is filtered to remove waste (faeces and sewage) and pathogens, to prevent disease

• High levels of oxygen for aerobic respiration are maintained by cleaning the water

• Fish are separated by age and size so that they do not eat each other (intraspecific predation) or fight

• Different species are separated to prevent fighting and interspecific predation

• Antibiotics are given to fish to prevent disease. Fish are also kept in small numbers to limit the spread of diseases

• Fish are given food that is high in proteins to ensure fast growth. They are fed frequently, so they do not start eating each other, but in small amounts, so they do not overeat

• Fish are given growth hormone

• Fish are separated by sex so that selective breeding can be used by farmers to ensure that only fish with desired characteristics can reproduce.

How does tobacco mosaic virus reduce crop yield

It prevents the formation of chloroplasts in leaf cells of tobacco plants (and other closely related plants, including tomatoes and peppers), and causes the leaves to change colour from green to yellow or white, in a mosaic pattern. This reduces the ability of the plant to photosynthesise, so the plant has less glucose, for respiration, to release ATP for growth, so it reduces crop yield.

Differences between mitosis and meiosis

• Mitosis produces two daughter cells, meiosis produces four

• Mitosis produces genetically identical cells; meiosis produces genetically different cells

• Mitosis produces diploid cells, meiosis produces haploid cells (it halves the chromosome number)

• Mitosis produces somatic cells; meiosis produces gametes

• Mitosis takes place anywhere in the body; meiosis takes place in the ovaries and testes only

Natural selection

There is variation in a population due to random mutations. A selection pressure in the environment will mean that some of these variations will give the organisms an advantage over the others in the population. This means that they are more likely to survive and reproduce, and pass on the alleles for the advantageous characteristic to their offspring. Over many generations, the advantageous allele will become more common in the population, so it has adapted to suit its environment.

Consequences of smoking on the circulatory system

Smoking can contribute to the build-up of plaque on the walls of arteries. When this occurs in the coronary arteries, it can lead to coronary heart disease, leading to a heart attack. Nicotine in smoke increases the risk of blood clots and high blood pressure, and carbon monoxide binds to haemoglobin in the red blood cells, which means that they can transport less oxygen around the body to respiring cells, so cells carry out less aerobic respiration, so they release less ATP energy, which can result in fatigue. The cells may carry out more anaerobic respiration, which produces lactic acid, which lowers the pH of the cells and blood and can lead to enzymes denaturing, and eventually, cell death.

Factors that increase the risk of coronary heart disease

• Diet containing too much saturated fat or salt

• Obesity (carrying extra weight puts a strain on the heart)

• Diabetes

• Lack of exercise

• Genetics

• Smoking/alcohol

• High blood pressure (damages arteries because the force of blood against artery walls increases)

• Stress

• Age

How are arteries adapted for their function

• Walls very thick

• Walls contain a thick muscle layer and elastic fibres

• To allow the artery to cope with the high internal pressure - it can expand, but will not burst, when high-pressure blood flows through

• Contains no valves

• Lumen diameter is fairly small

Structure and function of veins

• Walls are thin, as the pressure of blood is very low

• Contains valves to prevent the backflow of blood

• Lumen diameter very large

Structure and function of capillaries

• Walls are very thin - one cell thick - to provide a short diffusion distance for oxygen to diffuse out to respiring tissues, and carbon dioxide to diffuse in (the blood pressure is very low)

• Lumen diameter very small

Why does exercise affect heart rate

• Chemoreceptors on the aorta detect the increase in carbon dioxide concentration in the blood (from more aerobic respiration occurring)

• An electrical impulse travels from the chemoreceptors to the brain, and the medulla oblongata sends impulses down the accelerator nerve to the heart, so the heart rate increases

Adrenaline and heart rate, and its other effects

• When danger is detected, an electrical impulse travels from the brain to the adrenal glands on the kidneys, which release adrenaline into the bloodstream

• This activates a “fight or flight” response

• This increases breathing rate and heart rate (to provide more oxygen and glucose to respiring cells, so that they can carry out more aerobic respiration, releasing more ATP energy for muscle contractions; also removes carbon dioxide faster)

• Narrows small arteries in the small intestine, so that blood is redirected to the muscles in the limbs

• Dilates the pupil in the eye

• Stimulates glycogen to be converted into glucose in the liver

Adaptations of the pollen grains of insect and wind pollinated flowers

• Insect - large, sticky grains, with hooks to attach to insects’ bodies

• Wind - small, smooth and round to be easily carried by the wind, and many are produced

Adaptations of the placenta for efficient diffusion

• Large surface area, due to CHORIONIC VILLI

• Thin wall

• Rich supply of maternal blood vessels

What happens in the stages of mitosis

• Interphase - DNA in chromosomes doubles itself ready for mitosis

• Prophase - DNA in chromosomes condenses and becomes visible, and the membrane around the nucleus disappears

• Metaphase - the chromosomes line up at the equator of the cell

• Anaphase - the sister chromatids separate and become their own chromosomes, and are pulled to opposite ends of the cell

• Telophase - new nuclear membrane forms around the chromosomes at each end of the cell

• Cytokinesis - the cell membrane pinches in and divides into two daughter cells

Hormones vs neurotransmitters

Hormones produced in endocrine glands, carried in blood stream, all around body, long term effect