CB4 - Natural Selection and Genetic Modification

Evolution

A change in one or more characteristics of a population over a long period of time.

List the five different stages of human evolution discovered

Ardi, Lucy, Homo habilis, Homo erectus, Homo sapiens

How are stone tools dated from their environment?

Tools are found in different layers of rock, the lower the layer the older the tool.

How have tools created by human like species developed over time?

Tools have become sophisticated as time has gone on. The tools are better made and more suited to performing the task they were made for.

Cause of genetic variation

Characteristics of individuals vary due to differences in genes.

How do adaptations allow organisms to survive?

They provide organisms with an adventure against a selection pressure, meaning they outcompete other organisms to survive.

How does natural selection lead to the evolution of a new species?

The organisms that survive can reproduce and pass on the advantageous allele to their offspring. As more of these mutations occur the organism will eventually change enough that it becomes a new species.

Characteristics of the animal kingdom

Multicellular, cells have nuclei, no cell walls

Characteristics of the plant kingdom

Multicellular, have chloroplasts, cells have nuclei, cellulose cell walls.

Characteristics of the fungi kingdom

Multicellular, live on or in dead matter and feed on it, cells have nuclei, chitin cell walls.

Characteristics of the prokaryotes kingdom

Unicellular, cells do not have nuclei, flexible cell walls.

Genetic analysis

Looking at the genome of an organism and comparing their genes against others to see their similarities/differences.

Why do biologists often classify organisms into three domains?

Scientists discovered cells with no nuclei however genetic analysis showed they had genes more similar to plants and animals, therefore the three-domain system was introduced to show how closely related organisms are. Archea, Bacteria and Eukarya

Describe how new breeds and varieties collected?

Selective breeding is used to create new breeds with desirable characteristics. This could be for increased food yield, disease resistance or other advantages.

Genetically modified organism

An organism that has had new genes inserted into its DNA artificially after its genome.

How is selective breeding carried out?

An organism with a selected and bred. The offspring that display this characteristic are then selected and bred again. This continues over a number of generations to increase the expression of the desired characteristic.

What’s the impact of selective breeding on domesticated plants and animals?

Selective breeding has helped to create new varieties of plants and animals in order to give a desired set of characteristics. These include disease resistance, increased yield, flavour, coping with environmental conditions and faster growth.

Main stages of genetic engineering

Additional genes are added to a plasmid. Restriction enzymes are used to cut a useful gene out of an organisms DNA and the plasmid to form complimentary sticky ends, these are then joined together using a ligand enzyme. These plasmid vectors are then inserted back into the bacteria.

Uses of selective breeding in agriculture

Development of varieties of different plants for disease resistance, yield, crop growth speed and flavour.

Uses of GMOs in agriculture and medicine.

Creation of golden rice (rice that produces beta-carotene), this rice can be grown on poorer parts of the world where vitamin A deficiency is an issue (results in blindness).

Pigs are being produced that develop human-like organs for transplants.

Benefits of GMOs and selective breeding.

Creation of a variety of organisms that can cope with different selection pressures.

Risk of GMOs and selective breeding

GMO - Seeds from genetically modified plants are expensive. Could reproduce with wild plants, passing on their resistant genes. Some people believe that eating them is bad for their health (no evidence).

How to recognise binomial species named?

Organisms can be classified by their binomial names, the first representing their genus and the second their species. For example, humans are Homo sapiens so their genus is homo and their species is sapient.

How have fossil records provided evidence for human evolution?

Different stages show development of characteristics over time. Skull volume has increased, stood more upright as they walked on 2 legs, shorter arms as less need to climb trees.

How are organisms classified?

Organisms are classified into categories dependent on their characteristics, there are seven layers of organisation (kingdom, phylum, class, order, family, genus, species). The more categories of organisation two organisms share, the more closely related they are.

Explain how the development of resistance in organisms supports Darwin’s theory.

Bacteria in a population show variation in the amount of resistance they have to an antibiotic. When treatment starts, the ones with the alleles that make them most resistant will take longer to die. If the course of antibiotic is finished early, the resistant bacteria survive and pass on the resistant allele to their offspring.

Characteristics of Ardi from 4.4 million years ago

Smallest skull volume, shortest, long arms and big toes for climbing trees.

Characteristics of Lucy from 3.2million years ago

Larger skull volume, taller, walked upright, toes more like modern human.

Characteristics of homo erectus from 1.2million years ago

Much taller, larger skull volume, completely upright, shorter arms and feet (suggest they no longer climbed trees).