SB6 Flashcards Preview

Biology❌ > SB6 > Flashcards

Flashcards in SB6 Deck (49)
Loading flashcards...
1

How do plants make their own food?

Photosynthesis.

2

What’s happens during photosynthesis?

1. Photosynthesis organisms, such as green plants and algae, use energy from the sun to make glucose.

2. Some is used to make larger, complex molecules that the plants or algae need to grow.
These make up the organisms biomass.

3. The energy stored in the organisms biomass then works its way through the food chain as animals eat them and each other.
So photosynthetic organisms are the main producers of food for nearly all life on earth.

3

What is some of the glucose used for in photosynthesis?

Some is used to make larger, complex molecules that the plants or algae need to grow.
These make up the organisms biomass.

4

What is biomass?

The mass of living material.

5

What happens to the energy stored in organisms biomass?(photosynthesis)

The energy stored in the organisms biomass then works its way through the food chain as animals eat them and each other.
So photosynthetic organisms are the main producers of food for nearly all life on earth.

6

Where does photosynthesis occur?

It happens inside chloroplast - they contain chlorophyll which absorbs light.
Energy is transferred to the chloroplast by light.

7

What’s the equation for photosynthesis?

Carbon dioxide + water = (light)(chlorophyll) = Glucose + oxygen

8

What type of reaction is photosynthesis?

It’s an endothermic reaction - energy is taken in during the reaction.

9

What affects the rate of photosynthesis?

1. Light intensity.
2. Concentration of carbon dioxide.
3. Temperature.

Any of these can become the limiting factor

10

What’s meant by the limiting factor?

It’s stopping something (photosynthesis) from happening any faster.

11

What happens to the rate if there’s not enough light?

It slows down.

12

Explain how light affects the rate of photosynthesis?

1. Light transfers the energy needed for photosynthesis.

2. At first, as the light level is raised, the rate of photosynthesis increases steadily (the rate is directly proportional to light intensity). But this is only up to a certain point.

3. Beyond that, it wont make any difference - it’ll be either the temperature or the CO2 level which is the limiting factor.

13

Explain how CO2 affects the rate of photosynthesis?

1. CO2 is one of the raw materials needed for photosynthesis.

2. Increasing the CO2 concentration increases the rate of photosynthesis up to a point. After this it flattens out, showing that its no longer the limiting factor.

3. As long as light an CO2 are in plentiful supply then the factor limiting photosynthesis must be temperature.

14

What happens to the rate if there’s not enough CO2?

It slows down.

15

Explain how temperature affects the rate of photosynthesis?

1. Usually, if the temperature is the limiting factor it’s because its too low - the enzymes needed for photosynthesis work more slowly at a low temperature.

2. But if the plant gets too hot, the enzymes it needs for photosynthesis and its other reactions will be denatured.

3. This happens at about 45 degrees C.

16

What do root hair do?

They take in minerals and water.

17

Explain how root hairs take in minerals and water?

1. The cells on the surface of plants roots grow into ‘hairs’, which stick out into the soil.

2. Each branch of a root will be covered in millions of these microscopic hairs.

3. This gives the plant a large surface area fro absorbing water and mineral ions from the soil.

4. The concentration of mineral ions is usually higher in the root hair cells than in the soil around them, so mineral ions are absorbed by active transport, where as water is absorbed by osmosis.

18

What do phloem tubes transport?

Food

19

Explain how phloem tubes transport food?

1. Phloem tubes are made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through.

2. They transport food substances (mainly sucrose) made in the leaves to the rest of the plant fro immediate use or for storage.

3. This process is called translocation and it requires energy from respiration. The transport goes in both directions.

20

What do xylem tubes carry?

They take up water.

They also carry water and mineral ions, from the roots to the stem and leaves.

21

Explain what xylem tubes are made of and do?

1. They’re made of dead cells joined end to end with no end walls between them and a hole down the middle.
They’re strengthened with a material called lignin.

2. They carry water and mineral ions from the roots to the stem a leaves.

3. The movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream.

22

What is a transpiration stream?

The movement of water from the roots, through the xylem and out of the leaves.

23

What is transpiration?

The loss of water from the plant.

24

Explain water happens in transpiration?

1. It’s caused by evaporation and diffusion of water from a plants surface. Most transpiration occurs at the leaves.

2. The loss of water creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it.

3. This in turn means more water is drawn up from the roots, and so there’s a constant transpiration stream of water through the plant.

4. The transpiration stream carries mineral ions that are dissolved in the water along with it.

25

What are stomata needed for?

Gas exchange.

They allow CO2 and oxygen to diffuse directly in and out of a leaf, they also allow water vapour to escape during transpiration.

26

What are stomata?

They’re tiny pores on the surface of a plant. They’re mostly found on the lower surface of leaves.

27

Explain what guard cells do?

Stomata are surrounded by guard cells, which change shape to control the size of the pore.

When guard cells are turgid (swollen with water) the stomata opens.

When guard cells are flaccid (low on water and limp) the stomata are closed.

28

What environmental factors affect transpiration rate?

1. Light intensity

2. Temperature

3. Air flow

29

Explain how light intensity affects the rate of transpiration

The brighter the light the greater the transpiration rate.

Stomata begin to close as it gets darker photosynthesis cant happen in the dark, so they don’t need to open to let CO2 in. When stomata are closed very little water can escape.

30

Explain how temperature affects the rate of transpiration

The warmer it is, the faster transpiration happens.

When it’s warmer the water particles have more energy to evaporate and diffuse out of the stomata.