SB4 - Natural Selection and Genetic Modifications Flashcards
What is evolution?
Slow and continuous change of organisms’ inherited characteristics from one generation to another
Name the process that drives evolution
Natural selection
Name the scientist that came up with the theory of evolution
Charles Darwin
Explain the theory of evolution by natural selection
Genetic variation in a population gives some organisms a survival advantage over others when faced with certain selection pressures. The better suited organisms are more likely to survive, reproduce and pass on their beneficial alleles to their offspring
Whilst travelling, what did Darwin notice about individuals in a species?
There was variation in their characteristics
What did Darwin notice about each of the characteristics of the species he observed?
They were the characteristics that were best suited for that environment
Name the other scientist who also came up with the idea of natural selection
Alfred Russel Wallace
Explain why classification of living organisms is a result of evolution. All living things have a common ancestor
Organisms are classified according to how related they are
What is ‘selection pressure’?
The things that affect an organism’s chance of surviving and reproducing
Name two examples of selection pressures
Predation, competition for food, competition for water, competition for mates, disease
Explain how antibiotic resistance develops in bacteria
Some bacteria are more resistant to antibiotics than others. The more resistant bacteria survive longer when a person takes antibiotics. If people do not finish the antibiotic course, some of the most resistant bacteria will survive. They will then replicate and pass on antibiotic resistance to other bacteria
Why is antibiotic resistance in bacteria evidence for evolution?
It is an example of natural selection taking place that we can observe
What is a fossil?
A trace of an organism that lived a very long time ago - usually millions of years ago
Why are fossils important evidence to show how life has developed?
Fossils can be arranged in chronological order to show the gradual changes in the organism to show how species have changes and developed over billions of years
Why are there gaps in fossil records?
Most dead organisms are not turned into fossils - they decompose and therefore do not leave a trace
What are hominids?
Human beings and their ancestors
How did the skulls of hominids change over the past six million years?
Older skulls are smaller and more ape-like
What is Ardi’s species name?
Ardipithecus ramidus
How old is ‘Ardi’?
4.4 million years old
Describe the structure of Ardi’s feet and suggest what this says about her movement
She had ape-like big toe to grasp branches which suggested Ardi climbed trees
What does the structure of Ardi’s legs and arms suggest about her movement?
She had short legs and walked upright. She had long arms but didn’t use her hands to help her walk
What is Lucy’s species name?
Australopithecus afarensis
When did Lucy walk the planet?
3.2 million years ago
Who is closer related to humans: Lucy or Ardi?
Lucy
Describe Lucy’s feet that showed that she was more adapted to walking than climbing
Lucy had arched feet and no ape-like big toe
Where was a fossil of ‘Homo Erectus’ named ‘Turkana boy’ found in 1984?
Kenya
How old is the Turkana boy fossil?
1.6 million years old
How does the record of stone tools provide evidence for different ‘Homo’ species evolution?
Stone tools were very simple at first. At time passed the tools become more complex. Human brains must have been getting larger
Describe how the fossil of ‘Homo Erectus’ is different to Lucy
His short arms and long legs were more human-like in proportions, his brain size was larger than Lucy’s and more human-like, he was more adapted to walking upright compared to Lucy
When did ‘Homo Habilis’ live?
Between 2.5 and 1.5 million years ago
Describe the simple stone tools and how they were used by ‘Homo Habilis’
Simple tools called ‘pebble tools’ made by hitting rocks together to make sharp flakes that were then used to scrape meat from bones, to skin animals, and to crack bones open
When was ‘Homo Erectus’ walking the planet?
Between 2 and 0.3 million years ago
How were stone tools made by ‘Homo Erectus’ different to ‘Homo Habilis’?
Sculpting rocks into complex shapes allowed specialised tools to be developed, (e.g. simple hand-axes). Tools could be used for hunting, digging, copping and scraping meat from bones
When did ‘Homo Neanderthalensis’ live?
Between 300,000 and 25,000 years ago
Describe some of the more complex tools that ‘Homo Neanderthalensis’ used
Flint tools with sharp, pointed edges and wooden spears
When did the first ‘Homo Sapiens’ appear?
Around 200,000 years ago
Name some of the more specialised pointed tools that ‘Homo Sapiens’ were using from around 50,000 years ago
Fish hooks, needles and arrowheads
What is stratigraphy?
The study of rock layers
How do scientists use stratigraphy to date tools and fossils?
A tool or fossil must have been present at the time the layer of rock was formed. Older rock layers are usually found below newer layers of rock. Tools or fossils found lower down in deeper layers are usually older
If carbon is found in a fossil or tool, how can it be used to date the item?
Use Carbon-14 dating
Describe how the dating technique that uses carbon works
All carbon-based material contains a small amount of 14C which decreases over time. The amount of 14C is measured and can be used to date the object
How can rocks be dated using a radio metric dating?
Measuring the content of other radioactive compounds in the rock (e.g. potassium-argon and uranium-lead dating)
What is a pentadactyl limb?
A limb with five digits
How is the pentadactyl limb evidence for evolution?
The similarity of bone structure shows that species with a pentadactyl limb have evolved from a common ancestor
Name the five kingdoms used in classification
Animals, Plants, Fungi, Prokaryotes, Protists
Name the seven subdivisions of the five-kingdom classification method
Kingdom, Phylum, Class, Order, Family, Genus, Species [King Philip Came Over From Germany Swimming]
Name the subdivisions of the Three Domain classification system
Eukaryotes, Archaea, Bacteria
Explain why the three-domain classification system is more accurate than the five-kingdom classification method
Over time, technology has developed and DNA sequencing shows more detail about the interrelatedness of species
Explain why Carl Woese decided that the Prokaryote kingdom should be split into two groups
The DNA and RNA sequences of organisms in the Archae domain is different to the Bacteria domain
What is selective breeding?
When humans artificially select the organisms they are going to breed so that the genes for particular characteristics remain in the population
Why are organisms selectively bred?
To develop features that are useful or attractive to humans
Suggest two characteristics that cattle breeders would select for
Animals that produce more milk or more meat, or better tasting meat
Suggest two characteristics that crop farmers would select for
Plants with more disease resistance, more resistance to pests, increase size of crop, more drought resistance, more vitamins in crop, bigger fruit
List the four steps of the basic process of selective breeding
- Select individuals that have the desired characteristics
- Breed the selected individuals with each other
- Select the best of the offspring and breed them together
- Repeat the process over several generations to make the desirable trait stronger and stronger until all offspring have the desired characteristic
What can selective breeding be used for in agriculture?
Improve yields
Describe how selective breeding can be used in medical research into alcoholism
Researchers bred rats with either a strong preference for alcohol or a weak preference for alcohol. Researchers can compare the differences between the two different types of rats to help improve our understanding and possible treatment pathways
What is the main problem with selective breeding?
It reduces the gene pool - the number of different alleles in a population
The wild mustard plant has been selectively bred to produce a wide variety of vegetables. What characteristic was selected for to produce cauliflowers?
Clusters of flowers
What characteristic was selected for to produce Brussel sprouts?
Side buds on the stem
What characteristic was selected for to produce kohlrabi?
Swollen stem
What characteristic was selected for to produce cabbage?
A big bud at the top of the plant
What characteristic was selected for to produce broccoli?
Stems and flowers
What is ‘inbreeding’?
When people keep breeding from the ‘best’ animals or plants they end up breeding with closely related individuals
What can inbreeding cause?
Health problems - more likely to inherit harmful genetic defects when the gene pool is limited
Why is inbreeding a problem if a new disease appears?
The lack of variation in the population means that there is less chance of resistance alleles being present in the population
What is tissue culture?
When cells are grown on or in an artificial growth medium
Can tissue culture be used to produce whole plants from the cells of a single individual?
Yes
Can tissue culture be used to produce whole animals from the cells of a single individual?
No
Can tissue culture be used to produce animal cells and tissues from the cells of a single individual?
Yes
Give three advantages of plant tissue culture
Plants can be grown quickly, in very little space and grown all year around, clones will have the same beneficial features (e.g. pest resistance)
The plants produced via tissue culture are clones. What does this mean?
Genetically identical organisms
List the four steps to culture plant tissue
- Choose plant to clone based on its beneficial characteristics
- Remove several small pieces of tissue from the parent plant - fast-growing root and shoot tips are best
- Grown the tissue on a growth medium under aseptic conditions
- As the tissues produce shoots and roots, they can be removed and placed in potting compost to carry on growing
What are ‘aseptic conditions’?
Sterile conditions
Explain why aseptic conditions are important
To prevent growth of microbes that could harm the plants
Explain why animal tissue culture is often used in medical research
Scientists can carry out investigations on tissues in isolation to look at the effects of different changes on the cells of a single tissue. No animals are harmed during this process, reducing the number of animals needed for medical research
List the five steps to tissue culture animal cells
- Take a sample of the tissue to be studied from an animal
- Separate the cells in the sample using enzymes
- Individual cells are placed into a culture vessel containing growth medium
- After several rounds of cell division, the cells can be split up again and placed into separate vessels to encourage more growth
- Tissue culture can be stored to be used in the future
A scientist trying to save the rare plant species Wood Calamint from extinction decides to use tissue culture to grow more plants. Describe a method of tissue culture that the scientist would use
Take small pieces of tissue from the root and shoot ups of one of the remaining Wood Calamint plants. Grow the tissue samples under aseptic conditions in a growth medium that contains nutrients and growth hormones. Once shoots and roots start growing from the tissues, move them to potting compost to continue growing
Suggest one reason why the scientist chose to use tissue culture to save the Wood Calamint
New Wood Calamint plants can be grown quickly, in very little space, throughout the year, lots of plants can be grown from one parent plant, there are too few Wood Calamint plants for normal breeding methods
When viruses infect animal cells, they replicate inside them. To develop new vaccines against viruses, scientists need lots of animal cells. Explain why scientists use tissue culture to produce these cells
Scientists want to be able to study the effects of the vaccines on animal cells in isolation, they want lots of identical cells to test the vaccines on, to ensure a fair test
What is genetic engineering?
When a gene from one species genome is transferred into another organism’s genome in order to introduce a desirable characteristic
The genes for which characteristic has been inserted into a bacteria genome in order to help people with diabetes?
Genes to make the protein insulin
What is used to cut out the gene that is to be transferred during genetic engineering?
A restriction enzyme
How do restriction enzymes cut DNA at specific points?
Restriction enzymes recognise specific sequences of DNA and only cut the DNA at those points
What is a ‘sticky end’ produced during genetic engineering?
The end of the DNA strand that has unpaired bases
What is vector DNA?
Something used to transfer DNA into a cell
Give an example of a vector DNA
Plasmids (small, circular molecule of DNA)
What type of restriction enzyme is used to cut open the vector DNA?
The same restriction enzyme used to cut the gene from the original DNA strand
Explain why the same restriction enzyme used to cut the gene from the original DNA strand is so important
To ensure the vector DNA and the DNA being inserted have complementary sticky ends (complementary sticky ends)
Name the enzyme used to join the sticky ends of the gene and vector DNA together
Ligase enzymes
What do we call the two different bits of DNA once they are joined together?
Recombinant DNA
Once the gene and plasmids are joined together, what happens next during the process of genetic modification?
The recombinant plasmids are inserted into bacteria which are then grown in big vats of culture medium
Give an ethical concern about the genetic engineering of animals
It can be hard to predict what effect modifying a genome will have on an animal
Give a practical concern about growing genetically modified crops
Transplanted genes may get out into the environment, genetically modified crops might adversely affect food chains
Why could GM crops be a benefit as the world’s population is rising very quickly?
GM crops can increase the amount of food that a crop provides, some GM crops are able to grow better in drought conditions, GM crops could be engineered to contain certain nutrients, combatting deficiency diseases
What is ‘Golden rice’ and what can it prevent?
Rice that has been engineered to produce a chemical that the body converts into vitamin A, to prevent vitamin A deficiency which can lead to blindness
State a concern about genetically modified crops
Fears that countries could become dependent upon companies who sell GM seeds, even GM crops cannot survive in cortina areas where cops fail because the soil is so poor, worries about possibility of long term effects of exposure to GM crops
What does Bt stand for?
Bt stands for Bacillus thuringiensis which is a type of bacteria that produces a toxin that kills many insect larvae that harm crops
Describe how genetic engineers are using the gene for the Bt toxin
The Bt gene can be inserted into the genome of crops which then produce the toxin in their stems and laves. This makes them more resistant to insect pests
Explain how Bt crops can improve yield
Insects that usually eat the crops are killed by the toxin. Less plant gets eaten so it can photosynthesise more and grow faster
Explain how Bt crops reduce the need for chemical pesticides and why this is a benefit
Chemical pesticides can be harmful to good insects and the environment. Bt crops require less pesticide use because insects are killed by the Bt toxin
Give one concern about the use of Bt crops on the insects that feed on them
There is a danger that the insects will develop resilience to the Bt toxin
What can be added to poor soil to help plants grow?
Fertilisers
What do fertilisers contain?
Minerals like nitrates, phosphates and potassium
What problem can be caused by the excessive use of fertilisers?
Eutrophication
What can eutrophication cause?
Algal blooms and the death of aquatic organisms due to the absence of oxygen in the water
What are ‘biological control methods’?
Using other organisms (e.g. predators and parasites) to reduce the pest numbers
Which animal species was introduced to Australia to control beetles that were damaging sugarcane crops?
Cane toads
Which animal species can be used to control aphid populations?
Ladybirds and parasitic wasps
Explain why the animal species introduced to Australia is now a pest species itself
No native Australian predator species can eat the toads because they are poisonous
