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Flashcards in Biology IGCSE Deck (116)
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What is the placenta for?

Brings the mothers blood supply close to the blood supply of the foetus, allowing CO2, water and urea to diffuse from the baby to the mother and allowing glucose, amino acids and minerals to diffuse into the blood stream of the foetus


What is an experiment that determines the energy content in a food sample?

Measure the mass of the food. Place 20ml of water into a boiling tube. Measure initial temperature of the water. Spear food with a mounted needle and light it up with a Bunsen flame until it catches fire. Place burning food under tube of water. Keep relighting and doing the same until the food no longer burns. Measure the final temperature. Use the equation: Energy= 4.2 x Volume of water x Temperature change (divide by the change in mass of food as a comparative aid)


What does denitrifying bacteria do in the nitrogen cycle?

Reduce nitrates to nitrogen


What does the use of cloned transgenic animals have the potential for?

Allows mass production of useful chemicals (e.g. insulin, antibodies and even organs)


What causes mutations?

Inherited, exposure to ionising radiation, chemical mutagens


Why is it important for plant cells to be turgid?

It provides strength and support to the plant. Plants have a cell wall that stop them bursting when turgid. (When plant cells start to lose water they become flaccid, causing wilting. Flaccid cells can become plasmolysed when the cell membrane peels away from the cell wall, killing the cell)


What are the biological consequences of pollution of water?



How do vaccinations work?

They result in the manufacture of memory cells that enable future antibody production to occur sooner, faster and in greater quantity.


How are enzymes affected by pH?

After optimum pH, the active site of the enzyme changes shape (the enzyme is denatured) and stops being able to bind to the substrate.


What does nitrifying bacteria do in the nitrogen cycle?

Turn ammonium into nitrate (NO3)2-


Describe an experiment to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator.

Place hydrogen-carbonate indicator in four test tubes, with a leaf in three of them (one without is the control). Place one in the light, one in dark and one in dim conditions. The hydrogen carbonate indicator stays orange in normal CO2 conditions, turns yellow in high CO2 and purple with less CO2.


What should a balanced diet include?

Appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.


What is the role of the phloem?

To transport sucrose and amino acids between the leaves and other parts of the plant.


What is the role of the xylem?

To transport water and minerals from the roots to the leaves. The xylem consists of dead cells, and only move the water in one direction.


How is the bacteria Lactobacillus used in the production of yoghurt?

Lactobacillus uses lactose sugars in the milk to produce lactic acid by anaerobic respiration. The lactic acid affects the milk proteins, making the yoghurt curdle.


What does co-dominance mean?

Affect the phenotype equally in the presence of another co-dominant allele.


How does the eye focus on a far away object?

Incoming light is parallel so cilliary muscles relax and suspensory ligaments contract, the lens is pulled thin and light is refracted less.


Describe a simple experiment to demonstrate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.

Hydrogen-carbonate indicator solution turns from orange to yellow in the presence of CO2. An organism is placed on a gauze platform above the solution in a boiling tube.


What are the four main stages in the water cycle?

Transpiration, evaporation, condensation, precipitation


What are platelets for?

Clotting the blood to prevent infection and blood loss.


What does nitrogen fixing bacteria do in the nitrogen cycle?

Turns N2 (nitrogen) into ammonium (NH4+)


What causes energy requirements to vary?

activity levels, age and pregnancy


How do germinating seeds use food reserves until it can photosynthesise?

Seeds contain a small amount of carbohydrate and lipid which is used as a fuel to respire, providing the energy for growth. (The plant must grow leaves before the food store is used up)


How does the body carry out homoeostasis when it is hot?

Hairs on the skin lie flat (erector muscles relax), sweat, vasodilation (blood is diverted closer to the surface of the skin - arteriole opens)


When does respiration occur in plants?

All the time (day and night).


What are the conditions needed for seed germination?

Oxygen, water and correct temperature (warmth)


How does the eye respond to dim light?

Photoreceptors detect, radial muscles in the iris contract and ciliary muscles relax. The pupil diameter opens which allows more light to enter the eye.


How are developing embryo's protected?

Amniotic fluid


What do decomposers do in the nitrogen cycle?

Turn nitrogen in protein into ammonium (NH4+)


What does the term 'transgenic' mean?

The transfer of genetic material from one species to a different species.