Nutrition

• Organisms must obtain food to provide energy

  • Energy is necessary to carry out life processes e.g. movement, respiration and excretion

Nutrition in plants

• Plants use sunlight, carbon dioxide and water to produce oxygen and glucose in the process of photosynthesis

• Because plants create their own food for energy, they are described as being autotrophic

Nutrition in animals

• Animals consume other living organisms in order to obtain the energy they require

• They break down larger complex molecules into simpler molecules through the process of digestion

• As animals obtain their food from a range of different sources, they are described as being heterotrophic

Autotrophs make their own food whereas heterotrophs obtain it from a range of food sources.

Exam Tip

Sometimes understanding the origin of a word can help us to remember the meaning, for example:Autotroph comes from:

• 'auto' = 'self'

• 'trophic' = 'feeding'

Heterotroph comes from:

• 'hetero' = 'different'

• 'trophic' = 'feeding'

Respiration

• Respiration is a chemical reaction carried out in all living organisms

• Energy is released from glucose either in the presence of oxygen (aerobic respiration) or the absence of oxygen (anaerobic respiration)

• The reactions ultimately result in the production of carbon dioxide and water as waste products

• Energy is transferred in the form of ATP

Exam Tip

Make sure not to confuse respiration with gas exchange. Gas exchange involves getting oxygen into the cells and carbon dioxide out. Respiration uses the oxygen supplied from gas exchange to release energy in the form of ATP.

Sensitivity

• The sensitivity of an organism refers to its ability to detect and respond to stimuli in its surroundings

• Responding to the environment around them gives an organism the best chances of survival

Sensitivity responses in animals

• In humans, the nervous system provides a complex system of receptors, neurones and effectors which detect and respond to different stimuli using electrical impulses

• The endocrine system also allows a response to stimuli using chemical messengers, which travel in the blood, called hormones

The nervous system and endocrine system allow humans to respond to their environment.

Sensitivity responses in plants

• In plants, responses are controlled by chemicals and are usually much slower

  • Geotropism describes a plants response to gravity which causes the roots to grow down into the soil

  • Phototropism describes a plant's response to light which causes shoots to grow towards sunlight

Phototropism and geotropism allow plants to respond to their environment.

Movement

• Movement is an action by an organism causing a change of position or place

• The movement of an organism from place to place is called locomotion

• Plants cannot move from place to place but can change their orientation

  • For example, sunflowers track the sun and so change their orientation throughout the day

Sunflowers track the sun throughout the day.

Reproduction

• Reproduction is the process that leads to the production of more of the same kind of organism

• Reproduction is fundamental to the survival of a population and ultimately, the species

• There are different types of reproduction: sexual and asexual

Sexual Reproduction

• In this type of reproduction, the male and female gametes fuse together

  • In humans, the male gamete is the sperm and the female gamete is the egg

  • In plants, the male gamete is in the pollen grains and the female gamete is the ovule

• The DNA of the offspring is composed of both maternal and paternal DNA

Sexual reproduction involves the fusing of two gametes to form a zygote that contains DNA from both parents.

Asexual reproduction

• Cells or whole organisms can also reproduce using asexual reproduction

• Mitosis is an example of asexual reproduction

• There is only one parent involved so an exact clone is produced

• The DNA of offspring is identical to parental DNA

  • Plants can reproduce asexually through tubers, budding or runners

  • Single-celled organisms such as bacteria or amoeba reproduce asexually

    
    
    
    
    
    

Asexual reproduction in bacteria involves creating exact copies of the parent cell.

Control

Growth

Excretion