Topic 4 Flashcards
What is natural selection and how does variation affect natural selection?
Natural selection means ‘the survival of the fittest’. Individuals may have certain alleles which make them more likely to survive and reproduce whilst other individuals without those certain alleles may be less likely to survive and reproduce
Give 3 examples of selection pressures?
- Predation
- competition for resources
- disease
Describe the work of Darwin
- Came up with the theory of evolution through natural selection
- Noticed that there was variation in members of species and the different characteristics would make certain animals more likely to survive. (whilst on a voyage studying plants animals)
- Noticed that characteristics could be passed onto offspring
Describe the work of Wallace?
Provided further evidence for the theory of evolution e.g. butterfly warning colours to deter predators
How do bacteria provide evidence for evolution?
- In bacteria, there may be mutations in DNA sequence
- This can cause a bacteria to become resistant to antibiotics, meaning that they are more likely to survive and reproduce
- The resistant allele is passed down to other bacteria - natural selection
- The bacteria are better adapted to an environment with antibiotics and as a result antibiotic resistance is more common,
How has evolution influenced modern biology?
- Classification - If we know organisms have descended from one ancestor, then theyre all related and we can classify them
- Antibiotic resistance - we now understand the important of finishing a course of drugs/ not using them when unnecessary
- Conservation - we understand the important of genetic diversity and how it helps populations adapt to changing environments, which is why we have conservation projects
How do Ardi, Lucy and the turkana boy provide evidence to suggest humans evolved from chimpanzees
- Ardi: (4.4) Ape like big toe to grasp branches, long arms and short legs (walked upright and didnt use hands). Brain size - chimpanzees.
- Lucy (3.2) - Arched feet, adapted for walking. No ape like big toe. Size of legs and arms was inbetween ape and human. Brain size was slightly larger. (Walked upright)
- Turkana (1.6) - mixture of human and ape features. short arms, long legs. larger brain. walked upright
How did Homo habilis use tools? (2.5-1.5 million years ago)? (Oldest)
Made pebble tools by hitting rocks together to make sharp flakes. used to scrape meat from bones or crack bones open
How did Homo erectus use tools? (2 - 0.3 million years ago) second oldest
Sculpted rocks into shapes to produce more complex tools like simple handed axes to hunt, dig, chop and scrape meat from bones
How did Homo neanderthalis use tools? (300,000 - 25000 years ago) 2nd youngest
More complex tools. Flint tools, pointed tools and wooden spears
How do homo sapiens use tools? (200,000 - today)
Flint tools and pointed tools widely used. Arrowheads, fish hooks, and needles appeared around 50,000 years ago
What are three ways that scientists can figure out how old a fossil/ancient stone tool is?
- Looking at structural features of the tool or fossil. e.g simpler tools are likely to be older than more complex tools
- stratigraphy - study of rock layers. Older rock layers are found below younger layers. tools or fossils in deeper rock layers are usually older
- Stone tools are often found with a carbon containing material. e.g. a wooden handle. Carbon 14- dating can be used to date this material
How do pentadactyl limbs provide evidence for evolution?
The pentadactyl limb is common in many species but the functions have changed. The species may have come from a descendant with a pentadactyl limb but the functions may have changed due to evolution
What are the 5 kingdoms?
- Plants
- Animals
- Prokaryotes (single celled organisms without a nucleus)
- Fungi
- Protists (eukaryotic single-celled organisms e.g. algae)
What are the subdivisions after Kingdom?
Kylie puts carrots on famous grass species
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Why is the classification system quite out of date?
As technology has advanced, we are now able to compare how closely related organisms are through their DNA and RNA sequences. Through this, scientists have found that the Prokaryote kingdom are not as closely related as initially thought
Outline the 3 domains
- Archaea
- eukarya
- bacteria
What is the Eukarya domain?
The domain that includes a broad range of organisms including fungi, plants, animals and protists
What is the bacteria domain?
The domain that includes true bacteria that E.coli and staphyloccocus
What is the Archaea domain?
Organims that look similar to bacteria but are actually quite different through their DNA and RNA sequences. First found in extreme places like hot springs and salt lakes
Describe the process for selective breeding
1) From your existing stock, select the ones which have the characteristics you’re after
2) Breed them with each other
3) Select the best offspring and breed them together
4) Continue this process over several generations and the desirable trait gets stronger and stronger. Eventually, all the offspring will have the characteristic.
Give examples of features of organisms that are a result of selective breeding?
1 - Animals that produce more meat or milk
2 - Digs with a good gentle temperament
3 - Crops with disease resistance
4 - Plants that produce bigger fruit
Give an example of how selective breeding useful in medical research (in rats)?
Selective breeding has allowed scientists to compare the differences in behaviour and in the way the brains of rats work, that are bred with either a strong preference of alcohol/ or a weak preference of alcohol.
What are disadvantages of selective breeding?
- It reduces the gene pool (inbreeding) - reduces number of alleles in a population
- Not much variation - disease
- Inbreeding can cause health problems as there is a higher chance an organism can inherit a genetic defect when the gene pool is limited. e.g. pugs often have breathing problems.
Describe the process of tissue culture?
plants
1 - Choose a plant you want to clone - good characteristics
2 - remove pieces of tissue from parent plant (shoots or roots)
3 - Place in growth medium containing nutrients and growth hormones under aseptic conditions to prevent microbes growing that could harm plants
4 - can then be moved to potting compost where hundreds of clones can be made from just 1 plant
Describe how tissue culture of animal cells is carried out
- Extract sample of tissue you want to study e.g. from pancreas
- Cells in sample are separated from each other using enzymes
- Placed in culture vessel and bathed in growth medium containing nutrients allowing them to grow and multiply
- After several rounds of cell division , cells can be split up again and placed in separate vessels to encourage further growth
- Can then be stored for later use
How is animal tissue culture useful in medical research?
You can look at the effects of a particular substance or environmental change on the cells of a single tissue without complications from other processes in the organism
What are restriction enzymes?
Enzymes that recognise specific DNA sequences and cut the DNA at these points. The pieces of DNA are left with sticky ends
What are ligase enzymes?
Enzymes used to join 2 pieces of DNA together at their sticky ends
What is recombinant DNA?
The different bits of DNA together
What is a vector and what are the 2 sorts of vectors
A vector is something that’s used to transfer DNA into a cell. The 2 sorts are Plasmids and viruses.
Describe how genetic engineering works?
1) The DNA you want to insert. e.g. gene for human insulin is cut out with a restriction enzyme. The vector DNA is then cut open using the same enzyme
2. Both DNA are left with sticky ends. They are mixed with ligase enzymes and joined togther to make recombinant DNA
3. The recombinant DNA is inserted into other cells e.g bacteria
4) These cells can now use the gene inserted to make the protein we want. e.g. bacteria with human insulin gene can be placed in fermenter to grow in huge numbers and given to people with diabetes
How is genetic engineering useful in plants and animals?
1) Crops can be Genetically modified to be resistant to herbicides so that only weeds may be affected by the herbicides
2) Can transfer human genes that produce useful proteins into sheep and cows
What are the disadvantages of genetic engineering?
1 - It can be hard to predict what effect modifying its genome will have on an organism (health issues?)
2- Insects may become resistant to GM crops that produce toxins
3- transplanted genes may get out into the environment and create a ‘superweed’ variety
Give 2 examples of how GMO’s are useful in regards to food?
- Crops that are genetically engineered to be resistant to pests or to grow better in drought conditions can improve crop yields
- They can be used to combat certain deficiency disease (produce a chemical thats converted in the body to a vitamin)
Why may people not agree with using GMO’s to increase food production?
- Many people go hungry because they cant AFFORD food
- Some countries may become dependent on companies who sell GM seeds
- Sometimes, poor soil is the reason why crops fail
State 2 ways to increase food production, without using GMO’s
- Fertilisers
2. biological control
What do fertilisers do?
They replace the nutrients that have been lost from the soils to previous crops
What is biological control?
introducing other organisms to a habitat so that they can eat pests
Evaluate the use of biological control?
Pros:
- they have longer-lasting effects than GMO’s
- less harmful to wildlife
Cons:
- they can turn into pests themselves
