B5.2- Natural selection and evolution Flashcards
What did Gregor Mendel do?
Gregor Mendel carried out experiments on peas. He observed that phenotypic life characteristics such as height were all passed off from parent cells.
- characteristics in plants were determined by heridetary units (now called genes)
- Hereditary units are passed on from both parents, one from each pair from each parent
- Hereditary units are recessive or dominant
What is evolution?
Evolution is the gradual change of species over time. Scientist believe that we evolved from unicellular organisms that lived over 3 billion years ago
How do organisms evolve?
Organisms evolve through the process of natural selection. In a species there is often a wide genetic variation. When further mutations occur, genetic variation occurs. This genetic variation lead stp a range of phenotypes. The ones that possess beneficial phenotypes pass it onto their offspring through their genes. This is called survival of the fittest.
What are some examples of evolution?
- Peppered moths (evolved to suit black trees in industrial revolution)
- anti biotic resistant bacteria (conjugation through plasmids)
What are fossils?
Fossils are formed when plant or animal traces are left in the rock and undergo mineralisation when buried in sediment or tree sap
What is the fossil record?
The fossil layers that show how organisms have gradually changed over time.
How does the fossil record help us?
- Fossils of the simplest organisms such as bacteria are found in the older rock whereas the more complex organisms are in the newer fossils. This supports the theory that simple life form evolved into more complex ones
- Plant fossils appear before animal fossils, which is consistent because animals need plants to survive
- closely related organisms seem to have evolved from the same ancestor. We can tell by studying the bone structure
- the disadvantages however are that there are gaps in the fossil record where soft bodied organisms decomposed or fossils were destroyed due to earthquakes.
How was the theory of evolution formed?
Darwin went on a scientific expedition to the Galápagos Islands. During his time there he made famous observations on finches. He noticed that different islands had different finches, the birds were closely related but had different phenotypes. He realised that the birds were suited to the food on different islands. At the same time Russell Wallace was working in Borneo on his own theory. Wallace sent his discoveries to Charles Darwin and they released a joint presentation in 1858.
Why did people not believe the theory of natural selection?
There was not enough evidence to back up their hypothesis. Society was also very influenced by god and deemed his ideas blasphemous.
What is classification?
Classification is the process of sorting living organisms into groups. The organisms in the same groups share similar features. Scientists classify organisms to:
- identify species
- predict characteristics
- find or show evolutionary links
What’s an example of a single classification system?
The seven taxanomic levels kingdom,phylum, class, order, genus and species. Remember killing people could have gotten somewhere. They are classed into hierarchy levels.
What is binomial nomenclature?
Developed by Carl Linnaeus, a Swedish botanist. An example is Panthera leo, note that the genus has to have a capital letter.
What is artificial classification?
Organisms are classed into groups by their observable characteristics. The problem is that sometimes the classes overlap.
What is natural classification?
Natural classification is when organisms are put into groups based on their genome. This only possible with the technology that is available today which allows scientists to compare bases (codons in amino acids) within chromosomes, and class organisms that are genetically similar.
What is phylogeny?
Phylogeny is the study of evolutionary links via common ancestors. They are established by studying the similarities and differences in DNA. A phylogenetic tree shows us how it can be modelled.
