Well the lysosomes break down their food and the mitochondria releases stored energy.
Respiration
energy
in energy
They use it for respiration to release energy.
Fossil fuels wwwwwwwere once living plants and animals. If they were plants they got their energy from the sun, and if they were animals they got their energy from eating plants who got their energy from the sun, or from eating animals who ate animals who ate plants who got their energy from the sun. In other words the sun is the source of all energy. The sun´s energy is stored in living beings, in plants and the animals that eat the plants, and if conditions are right, that energy is then stored in the form of fossil fuels.
Its to release excess energy that they have stored up.
Energy is stored in the chemical bonds of various molecules. The most common is called ATP (adenosine triphosphate) and this molecule is transferred from the plants and can be used in the animals.
respiration
Animals use their stomach and then enzymes to release the energy stored in food. This energy is formed into high energy compounds like adenosine triphosphate (ATP).
No "thinking" required here: plants preceded animals by eons. The reason is energy. Plants store it; animals burn it up. The processes are called synthesis (photosynthesis, if the energy is in the form of light) and respiration. Stored energy has to be built up before it can be used. Animals get that energy from plants by eating them.
When glucose gets broken down in animals and plants during respiration, stored energy is released in cells.
glucose is the stored energy in animals
Animals take the energy from plants, reprocess it, and transfer it into chemical, mechanical, and thermal energy. And after the animals die, the energy they stored is broken down by tiny organisms, absorbed into the soil, and then used by plants to grow. The circle of life.
The process' (2) in which energy is stored in the form of glucose are photosynthesis and also cellular respiration. Photosynthesis takes place in plants and cellular respiration in both plants and animals.