Examples of Natural Selection Because evolution by natural selection generally happens over millions of years, it is difficult to see it taking place, and we often have to rely on evidence from the...
Overproduction of Offspring The number of offspring, or young, produced in each breeding event differs between species Some species produce small numbers of young, e.g. elephants usually give birth...
Variation Differences exist between organisms of the same species These differences are known as variation Examples of variation include: Coat colour in mammals Body length in fish Flower colour in...
Evidence for Evolution: Fossils Fossils are the preserved remains of organisms, or the traces left by organisms, such as footprints, burrows and faeces These remains can be preserved, e.g. in rocks...
Evolution Defined Species do not stay the same over time; the species that we see around us today have developed over millions of years This process of species change is known as evolution Evolutio...
Drawing the Carbon Cycle The many processes by which carbon is transferred from one store to another are collectively known as the carbon cycle During the carbon cycle, carbon is present in both or...
Industrialisation & Increased Carbon Dioxide Atmospheric carbon dioxide levels have fluctuated throughout Earth's history due to events such as volcanic eruptions and the weathering of limeston...
Greenhouse Gases & Climate Patterns Greenhouse gases absorb infrared radiation emitted by the earth, causing the atmosphere to warm Without greenhouse gases, the earth would be much colder The ...
The Main Greenhouse Gases When radiation from the sun hits the earth, it is radiated back from the earth's surface as long-wave radiation A greenhouse gas is a gas that absorbs this re-radiated rad...
