Topic 4-Natural selection and Genetic modification

Page 1

CB4: Natural selection and genetic modification

CB4a-Evidence for human evolution

Evolution is the slow and continuous change of organisms from one generation to the next.

Binomial species names are a species' genus name followed by its species name in Latin. For example: humans are Homo sapiens.

Evidence from human evolution can be seen from fossils of both previous related species as well as tools. The larger the skull size of an ancestor, the more intelligent they were. Also, arm length suggests whether they were still climbing in trees. The development of tools often shows the development of the species' intelligence. Therefore the newer the species, the more advanced the tools, the shorter the arms and the bigger the skull.

Stratigraphy is the way of finding out how far the stone tools date back to. Older rock layers are often found below newer rock layers. Carbon-14dating can be used to date this material.

One of the oldest stone tools would have been simple, like pebbles. They would have been hit together to form a spark, used to scrape meat of bones or break bones apart. Moving to younger tools, they would have been carved a bit more to resemble simple hand axes. As time goes on, the tools would get more complex in shape until they found arrowheads which show early Homo sapien work.

Ardi is a species called Ardipithicus ramidus. They lived 4. million years ago. Ardi had long arms and short legs for swinging in trees, hand-like feet to grip branches, her brain was very small and her pelvis suggests she could walk upright. Her hand bone structure suggests she didn't use her hands to help her walk. Lucy is an Australopithecus afarensis. She was dated from 3.2 million years ago. She is more human like than Ardi: her feet were more arched and human like, her arms were shorter and legs were longer, her brain was slightly larger but not by much and she walked upright. The Homo erectus species date back to 1.6 million years ago. Their features are more humal-like than Lucy: short arms, long legs, bigger brain size and they walked upright.

CB4b-Darwin's theory

Genetic variation is caused by mutation and sexual reproduction.

Organisms adapt to their environment so that they are protected from predators and can survive longer.

Natural selection allows some to survive better than others due to their adaptations and ability to compete for resources.

Natural selection changes the adaptations of an organism which can be inherited over time which leads to a new species eventually.

Development of resistance in organisms shows Darwin's theory that a species will change over time in order to be better suited to its environment; in this case being an organism developing a resistance to something over time.

CB4c-Classification

The classification order is: Kingdom, Phylum, Class, Order, Family, Genus, Species. This order starts from different kingdoms and then breaks down different species.

Animals are multicellular organisms that do not have cell walls and do have nuclei. Plants are multicellular organisms that do have cell walls made of cellulose and have nuclei and chloroplasts. Protists are unicellular organisms that have a nucleus and some have cell walls. Fungi are multicellular organisms that have cell walls and nuclei but not chloroplasts . They feed saprophytically. Prokaryotes are unicellular organisms that have no nucleus and flexible cell walls.

Genetic analysis is when someone analyses an organism's genetics.

Biologists classify organisms into 3 domains because some species have no nucleus but do have unused sections of genes. These are called Archaea. Bacteria and Eukarya are the other two.

CB4d-Breeds and varieties

New breeds and varieties are created because, if there is a disease, not all breeds and varieties will be wiped out as some may be immune to the disease.

A genetically modified organism is an organism that has been selectively bred so that it contains favourable characteristics.

Selective breeding can be carried out by both genetic engineering (the replacement of certain genes) or by choosing which organisms have favourable characteristics in order to have a chance of the offspring having the characteristics.

The offspring can have health problems as inbreeding as certain animals have the same characteristics and their offspring can have a disease they are both carriers of.

CB4e-Genes in agriculture and medicine

Genetic engineering: restriction enzymes recognise specific sequences of DNA and cut the DNA at these points. The pieces of DNA are left with sticky ends where they have been cut. Then, Ligase enzymes join the two sticky ends together. These two bits of DNA that are now together are known as recombinant DNA.

In selective breeding there are uses in agriculture such as: Some cattle will have a higher yield of meat than others. Also, some sheep are selectively bred to have a higher wool yield. However there are drawbacks such as: It reduces the gene pool. This means that there are fewer alleles and then all allels are similar and a disease can wipe out the organisms.

In genetic engineering there are uses in agriculture such as: crops can be genetically modified in order to be resistant to herbicides. Therefore farmers can kill the weeds without affecting the crops which leads to a higher crop yield. However there are drawbacks such as: Transplanted genes can get out into the environment e.g. herbicide resistant genes can be picked up by weeds and then the weeds become herbicide resistant too. Also, gm crops are not good for the food chain and are not that healthy.