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.
