Food Chains and Food Webs

Food Chains

• Food chains show the transfer of energy between organisms, the arrows represent the direction of energy transfer.

• A food chain consists of a producer, a herbivore, a carnivore and an apex predator.

• The producer is a plant which makes its own food.

• The herbivore is a type of consumer which eats the producer.

• The carnivore is a type of consumer which eats other animals.

• The apex predator is the last link in the food chain, which eats the carnivore,

• Bioaccumulation- The build up of chemicals, like insecticides, passed along a food chain.

Food Webs

• Food webs show how lots of food chains are connected in an ecosystem.

Populations and Ecosystems

• A population is the number of organisms who live in the same area.

• Populations of organisms are constantly changing, which affect other populations in a food web.

• Aerobic Respiration

  • This is with oxygen.

  • The word equation for aerobic respiration is glucose + oxygen → carbon dioxide + water ( + energy).

  • Aerobic respiration occurs in the mitochondria of cells in order to transfer energy.

  • Mitochondria- small structures in a cell which make most of the energy for the cell.

  • Glucose is absorbed from the small intestine into the blood plasma. It is transported into the cells where it diffuses in.

  • Blood plasma- the liquid component of your blood, which contributes to just over 50% of your blood’s volume.

  • Oxygen is breathed in, then it diffuses into the bloodstream. Oxygen is then carried by haemoglobin to the cells where it diffuses in.

  • Haemoglobin- a red pigment which binds with oxygen in order to carry oxygen to where it is needed for respiration.

  • Carbon dioxide then diffused out of the cells and into the blood plasma. After that, it is transported to the lungs where it diffuses into the alveoli and is exhaled.

  • Alveoli- multiple air sacks which are inside your lungs. Alveolus is the singular version of alveoli.

  Anaerobic Respiration

  • This is without oxygen.

  • The word equation for this is glucose → lactic acid ( + energy).

  • Anaerobic respiration happens when there is not enough oxygen for aerobic respiration, such as intensive exercise.

  • It transfers less energy than aerobic respiration.

  • The lactic acid produced can cause muscle cramps. This causes increased inhalation to break down lactic acid – the oxygen needed is called the oxygen debt.

  • It can take a few hours from a normal exercise, to several days after a marathon in order to pay back an oxygen debt.

  Fermentation (in microorganisms)

  • The word equation for this is glucose → ethanol + carbon dioxide ( + energy)

  • Yeast respires anaerobically, the fermentation is important in food production.

  Photosynthesis

  • Photosynthesis is a chemical reaction that takes place in the chloroplast to produce glucose.

  • The word equation for photosynthesis is carbon dioxide + water → glucose + oxygen. The symbol equation for this would be Co2+h2o → c6h12o6+o2.

  A leaf’s adaptation for photosynthesis

  • Leaves have a lot of chlorophyll, which absorb light for photosynthesis and are responsible for the green colour in a leaf.

  • They are thin in order for gases to be able to diffuse in and out of the leaf.

  • They have a large surface area so they can absorb as much light as possible.

  • They have veins, these are the vascular tissue of the leaf and are located in the spongy mesophyll.

  • The vascular system has two types of tissue, xylem and phloem.

  • The xylem distributes water and dissolved minerals upward through the plant, from the roots to the leaves, while the phloem carries glucose downward from the leaves to the roots.

  Minerals

  • The minerals plants need for growth are nitrates, phosphates, potassium and magnesium.

  • Nitrates for growth.

  • Phosphates for healthy roots.

  • Potassium for healthy leaves and flowers.

  • Magnesium for making chlorophyll

  • If a plant does not have enough of a mineral, it may suffer from a mineral deficiency. Farmers can use fertilisers to add missing minerals to the soil.

  • Symptoms of mineral deficiency in a plant are stunted growth, purple-red colouring, chlorosis, Interveinal Chlorosis and Chlorosis.

  • Chlorosis- The loss of the green colour in plants, this is due to them producing insufficient chlorophyll. Leaves with chlorosis are often pale, yellow or a pale yellow. This is caused by iron deficiency.

  • Interveinal Chlorosis- A yellowing of the tissue in between the veins due to the leaves producing insufficient chlorophyll. Unlike Chlorosis, the veins are still green.

  Chemosynthesis

  • Chemosynthesis is when bacteria use a variety of chemical reactions to make their own glucose.

  • Unlike photosynthesis, it does not use sunlight as the energy source, it uses chemicals.

  • The word equation for chemosynthesis is- Carbon Dioxide + Water + Hydrogen Sulfide → Glucose + Sulfur Compounds

  • The symbol equation for chemosynthesis is 18H2S + 6CO2 + 3O2 → C6H12O6 (carbohydrate) + 12H2O + 18S.

Other Key Words

• Prey- An organism which is eaten by another organism.

• Predator- An organism that eats another organism.

• Interdependence- When living organisms depend on each other to survive, grow, and reproduce.

• Ecosystem- All the organisms found in a particular location, and the area they live in.

• Community- The organisms in an ecosystem.

• Habitat- The area a community lives in

• Niche- The particular place or role that an organism has within an ecosystem. This reduces competition for resources.