CB4 - Natural Selection and Genetic Modification

• Explain Darwin's Theory of Evolution by Natural Selection

  Darwin proposed that a species evolves over time through the process of natural selection, where the variations within an organism's species allow a particular to cope with environmental change - individuals with more advantageous traits are more likely to survive and reproduce, passing such traits to their offspring.
• How did Darwin use resistant organisms to support his theory?

  Antibiotic resistant bacteria is an example of evolution by natural selection. In a population of bacteria, a variation within the species allow some to be more resistant to an antibiotic than others. When someone stops taking an antibiotic too early, resistant bacteria (which are still alive) have time to reproduce, evolving and becoming more resistant.
• How old is Ardi?

  4.4 million years
• How old is Lucy?

  3.2 million years ago.
• What are Ardi's main characteristics?

  She was 1.2 m tall and 50 kg. She had long arms and very big toes which allowed her to climb trees. Her leg bones show that she may have been able to walk upright.
• What were Lucy's main characteristics?

  She was 1.07 m tall, she could probably walk upright, but although her toe bones were arranged in the same way as those of modern humans, they were much more curved.
• How old were Richard Leakey's fossils, Homo Erectus?

  1.6 million years ago.
• What were the main characteristics of the Homo Erectus and what did they prove?

  They were tall, standing at 1.79m and strongly built, and provided evidence that humans evolved in Africa.
• How do the development of stone tools serve as evidence for human evolution?

  Scientists can work out the ages of different layers of rock, which were use to make stone tools million years ago - they assume that a stone tool is about the same age as that layer of rock.
• How did genetic analysis lead to the suggestion of the three domains rather than the five kingdoms?

  Initially, scientists classified organisms based on what their cell looked like, placing them on a kingdom. However, scientists, whilst analysing the genetics of organism found characteristics in prokaryotes that overlapped with multiple groups, complicating classification models. Thus, the proposition of three domains instead of five kingdoms.
• What are the five kingdoms?

  Animal, Plants, Protists, Prokaryotes, Fungi
• What are the three domains?

  Bacteria, Archaea and Eukarya
• Which kingdoms have multicellular organisms?

  Animals, plants and fungi
• Which kingdoms contain unicellular organisms?

  Protists & Prokaryotes
• What are the characteristics of each domain?

  Archaea - cells with no nucleus and genes that contain unused sections of DNA

  Bacteria - cells with no nucleus, no unused sections in the genes

  Eukarya - cells with a nucleus, unused sections in genes
• What is selective breeding?

  Selective breeding is a process where specific organisms are chosen due to their desired characteristics, and bred together to enhance desirable traits such as disease resistance or yield.
• What are the consequences of selective breeding?

  Although selective breeding, over time, allows for the production of new breeds of animal species and new varieties of plant species, it negatively impacts less desirable and weaker species due to natural selection, leading to their extinction. Also, since selectively bred organisms are very similar, a change in condition may affect all organisms and lead to mass extinction of such specie.
• What is genetic engineering?

  Genetic engineering is the process which involves modifying the genome of an organism to introduce desirable characteristics.
• What are some issues with genetic engineering?

  Seeds for genetically modified (GM) crops are expensive. Some people think that GM crops will reproduce with wild plant varieties and pass on their resistance genes, however also carrying unknown consequences in wild plants. Also, some people believe eating GM organisms may be bad for our health.
• The main stages of genetic engineering:

  1. Scientists use restriction enzymes to cut a useful gene out of an organism's DNA
  2. This cutting leaves strands of DNA with sticky ends, where some sections have unpaired bases
  3. If two sticky ends match, they can be joined together using an enzyme called ligase.
  4. Any DNA molecule used to carry new DNA into another cell is called a vector.