5.3 Fertilisers

5.3 understand the use of fertiliser to increase crop yield



Fertilisers are used to stimulate the growth of plants.
Fertilisers usually come in the form of phosphate and nitrates which are absorbed by plants through the soil.
Fertilisers can be divided into two groups: organic and artificial

Organic are usually waste from farming such as cow faeces.

artificial fertilisers can come in the chemical form of potassium nitrate or ammonium nitrate.

5.2 Crop Yield

5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses



crop yield is governed by the rate of photosynthesis.
CO2 is a substrate in the reaction of photosynthesis.
by increasing the amount of carbon dioxide, the products of photosunthesis will also increase until it reaches a point where it can go no further.

in comparison, increasing temperature will also increase the rate of photosynthesis until it reaches the optimal temperature. if temperature increases any further, the rate of photosynthesis will slow down.

5.1 Glasshouses

5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops.



Glasshouses/Greenhouses
-they are usually built on a framework and are covered in glass to allow light to pass through.

Polythene tunnels are a cheaper alternative to this using polythene instead of glass.

How it works:
1. solar radiation (light) enters the glasshouse
2. light energy passes through glass
3. energy is absorbed by surfaces inside the glasshouse
4. the energy is re-emmited as heat which warms air inside the glasshouse
5. this provides the optimal temperature for crop production and keeps conditions constant throughtout the year.
6. it also helps to keep water levels constant.

2.85

describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

2.84

understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

2.83

recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

2.82

describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

Hormones: are produced by endocrine glands and is released directly into the bloodstream where it easily finds its target cells at a small distance from the point of release.

Neurotransmitters are secreted by vesicles in the synaptic bulb and travel across the synapses of neurons as opposed to hormones traveling in the bloodstream.

2.77b Thermoregulation

understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are examples of homeostasis.

Homeostasis uses a negative feedback loop to control or maintain constant conditions inside the body.

Receptor(Hypothalamus in brain) ---> co-ordinator (body temperature 37C) ----> effector (skin)
Response (decrease of body temperature) ---> stimuli (temperature of blood) ---> Receptor

2.77a Thermoregulation

understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are examples of homeostasis.

Homeostasis refers to a constant of conditions.
Homeothermic means the same temperature.

Homeothermic organisms have a constant body temperature in relation to environmental temperature. They maintain this condition by usage of a process called thermoregulation.
Mammals maintain a constant body temperature because the optimal temperature of their enzyme catalysed biological reactions is approximately the same as their body temperature.

2.76 Sensitivity

Understand that organisms are able to respond to changes in the environment.