Biology B2: Organisms in the environment

How do algae absorb Carbon Dioxide?

Algae absorb CO₂ from the water around them.

How are leaves adapted for photosynthesis?

1. Broad leaves for high exposure to light for chlorophyll. 2. Contain chlorophyll in chloroplasts to absorb light energy. 3. They have stomata to allow Carbon Dioxide in and Oxygen out. 4. Veins to transport water to cells of leaves from roots.

What are the processes of photosynthesis?

1. Light energy is absorbed and converted by chlorophyll in cholroplasts in plant leaves into chemical energy. 2. This energy is used to convert CO₂ into glucose. 3. Oxygen is produced as a by-product.

Which limiting factors affect rate of photosynthesis?

1. Light is limited to daytime hours. 2. Temperature speeds up reactions but mustn't be too high (enzymes can denature). 3. Carbon Dioxide is often used up in the daytime, limiting photosynthesis.

What do plants do with the glucose they make?

1. Respiration. 2. Converting glucose into insoluble starch for storage. 3. Strengthening cell walls by producing fats, protein or cellulose. 4. Producing fats and oils to store energy.

How could you show that a plant is storing starch?

By testing the plant with iodine solution, you can test for starch. If the iodine turns dark blue, test is positive.

How is glucose stored in plants when not in use?

Glucose is stored as *insoluble starch*.

What are the drawbacks of using a hydroponics growing system?

Hydroponics is very expensive and requires masses of energy.

What are the main benefits of a hydroponics growing system?

Hydroponics systems increase growth rates and increase crop yields. They can be used where land is poor and it produces crops that don't need to be ploughed or cleaned. High crop yields mean that profits can be very high.

How can we test for starch and therefore photosynthesis in plants?

Iodine solution turns dark blue.

What is the equation for photosynthesis?

Light + Water + Carbon Dioxide → Glucose + Oxygen

Which minerals do plants need to build amino acids for protein?

Plants need nitrate ions and mineral ions to build amino acids for protein creation.

What happens to the glucose produced during photosynthesis?

Some of the glucose produced in photosynthesis is used immediately by plant cells. However, most glucose is *converted into insoluble starch and stored*.

Where is starch stored in plants?

Starch is stored in the cells of the leaves and sometimes in bulbs.

Why is starch stored by plants?

Starch is stored so that energy is not wasted when it's not needed. It provides an energy store for when light levels are too low for photosynthesis.

Why do plants grow quicker in a greenhouse?

Temperature is higher in a greenhouse so chemical reactions are quicker and enzymes work at optimum.

Which physical factors affect distribution of organisms?

Temperature, availability of nutrients, amount of light, availability of water, availability of carbon dioxide and oxygen.

How does a plant receive the water and carbon dioxide it needs for photosynthesis?

Water - roots & stomata. Carbon Dioxide - stomata. Light - Chlorophyll in chloroplasts.

How can we overcome the limiting factors of plants?

We can artificially manipulate light, temperature and carbon dioxide in green houses to increase rate of photosynthesis.

How can we measure the distribution of living things?

We can measure distribution of living things by using quadrats randomly and along a transect.

What is photosynthesis?

When plants absorb light energy and convert it into food.