B15 Genetics and evolution Flashcards
Who was Gregor Mendel and what did he discover?
He was an Austrian monk who carried out breeding experiments on peas.
One of his observations was the inheritance of each characteristic is determined by ‘units’ that are passed on unchanged to descendants
What was observed of chromosomes in the late 19th century?
Behaviour of chromosomes during cell division
Why were Mendel’s ideas initially disreguarded?
- no one knew about genes or chromosomes
- people didn’t understand his theory
How did the idea of genes become linked to Mendel’s discoveries?
- early 20th century
- chromosomes and Mendel’s units behaved similarly-> idea that units (now called genes) were located on the chromosome
What happened in Mid-20th century about DNA?
The structure of DNA was determined + the mechanism of gene function
What is the gene theory?
the effect of genes is that they code for proteins
- developed through the scientific work of many scientists (Rosalind Franklin, Maurice Wilkins, James Watson, Francis Crick)
What does Darwin’s theory of evolution by natural selection tell us?
All species of living things alive today have evolved from the first simple life forms
Who was Lamarck? + What was his theory of evolution?
Jean-Baptiste Lamarck was a French biologist
His theory: (‘fountain of life’)
-the way organisms behaved affected the features of their body
-changes that occur in an organism during its lifetime can be inherited
ie if a giraffe stopped using its long neck, its neck would shrink and be lost
What were the faults in Lamarck’s theory?
- no evidence for ‘fountain of life’
- people didn’t like the idea of being descended from worms
- could clearly see flaws (ie parent’s big muscles aren’t inherited by children)
Who is Charles Darwin? + How did he come up with his theory of evolution?
Scientist
1831, ship geologist + naturalist, 22 years old, on world voyage to South America
South America- discovered new form of rhea, noticed slight differences between ostrich and rhea
Galapagos Islands- noticed species varied from island to island. Strong similarities between different finch types on the different islands-> adapted to local conditions
Collected specimens of animals and plants, detailed drawings, written observation during voyage
What were Darwin’s main ideas after returning to England
- The individual organisms in a particular species tend to show a wide range of variation for each characteristic
- Reproduction always gives more offspring that the environment can support-> organisms that inherit characteristics most suited to the environment (‘fittest’) are most likely to survive and breed successfully
- When they breed, they pass on characteristics that enable them to survive to the next generation
What is Natural Selection?
The process by which evolution comes about
What was evidence Darwin used for his theory?
- used animals and plants seen on his journeys, noting organisms on different islands that adapted to their environments-> showing evolution
- carried out breeding experiments with pigeons
- studied different types of barnacles
Why did people object Darwin’s ideas?
- challenged the belief that God made all the animals and plants on earth
- lack of evidence for scientists to support the theory
- no way to explain variety and inheritance at the time (genetics) -> hard for people to understand and accept
Who was Alfred Russel Wallace? + What was his work?
1848, expedition to South America with Henry Bates
- on his returning trip, his collection was destroyed by fire so he went on another trip
- he discovered an understanding that forms of a species poorly adapted to change were likely to die out, leaving the better-adapted forms to survive and breed
- he published joint writings with Darwin in 1858
- his work provided a starting point for our understanding of speciation
What is Genetic variation?
a population of species containing a wide range of alleles controlling its characteristics resulting from sexual reproduction and mutation
What is the process of Speciation?
- 2 groups of a species become separated
- there is genetic variation between the populations
- different natural selection takes place in each group
- eventually become so different they are no longer able to interbreed successfully to produce fertile offspring
What is the definition of Speciation?
Where populations become so different that successful interbreeding is no longer possible
How do populations become isolated?
Geographical isolation: 2 populations become isolated by a geographical factor (new mountain range, new river)
Earthquakes (separate land), volcanoes (create new land)
Environmental isolation: climate changes in one area where the organism lives, not the others. (flowering times, therefore breeding times of the population and species linked to it, change)
What are fossils?
the remains of organisms from millions of years ago, found preserved in rocks, ice and other places
Why might an animal or plant not decay when it dies?
One or more of the conditions for decay are not present
- little or no oxygen present
- poisonous gases kill off bacteria that cause decay
- temperature is too low for decay
How can animals be preserved almost intact? + What is the importance of this?
Within ice or peat
- insight into the looks of the animal
- the diet of the animal, colour of the flower
- extract DNA + compare to modern organism DNA
What replaces the harder parts of the animal or plant when forming some fossils?
Harder parts of the animal or plant are replaced by minerals as they decay and become part of the rock
- over long period
How are mould fossils formed?
an impression of an organism is made in the mud and then becomes fossilised
How are cast fossils made?
When a mould of a fossil is filled in
What is the most common form of fossil?
Rock fossils
How is a fossil formed?
- organism dies and falls to the bottom of the ocean
- the flesh rots/is eaten away by smaller organisms-> leaves the skeleton to be covered in sand or soil and clay
- over time the layers build up over the skeleton, increasing the pressure
- eventually the layers of sediment turn into rocks and forms cracks, letting small rocks and ground water through, breaking down the skeleton by mineralising it
- eventually the earth rock shifts (tectonic activity)
- the fossil emerges as the rocks move
What are examples of fossils that aren’t actual organisms?
- Fossil footprints, burrows, rootlet traces, droppings
- help understand life on Earth long ago
Why is the Fossil record incomplete?
- many early life forms were soft-bodied organisms-> little fossil trace
- majority of fossils formed in early life have been destroyed by geological activity (mountain range formation, erosion, earthquakes, volcanoes)
- most organisms that died didn’t become fossilised-> RARE conditions for fossilisation
- many fossils are yet to be found
What can complete fossil records show?
- How some organisms have changed and developed over time
- reconstruct ecology, climate and environment of a million years ago
What is Extinction?
The permanent loss of all the members of a species
What are the causes of Extinction?
Always involve change in the environment of an organism
- change in temperature
- new predators
- new diseases
- new, more successful competitors
- changes to the environment
- single catastrophic event (volcanic eruption)
How can living organisms cause extinction?
- New predators wipe out unsuspecting prey animals if prey animals lack adaptations to avoid them
- New predators can evolve
- Existing species moves into new territory
- New diseases can bring a species to point of extinction
- One species can cause another to become extinct by successful competition-> new mutations can give a species an advantage over another
What is geological time?
changes in the environment and climate of the earth over millions and billions of years
What are the main causes of extinction in history?
changes to the climate or the environment
What is the usual cause for mass extinction?
A single catastrophic event
- colossal volcanic eruption
- collision of giant asteroids
What destroyed the dinosaurs?
Most recent mass extinction- 65 million years ago
- giant asteroid collided with earth in Mexico
- impact caused huge fires, earthquakes, landslides, tsunamis
- dust in the atmosphere made everything dark
- 50%-70% of all living species became extinct
ALSO THEORY
- drop in sea temperature (about 9 degrees) triggered mass extinction
SCIENTISTS ARE NOT FULLY SURE
How can bacteria develop resistance to antibiotics?
They have a natural mutation (change in genetic material) meaning they aren’t affected by the antibiotic
- mutations happen by chance, produce new strains of bacteria by natural selection
Why can bacteria evolve rapidly?
They reproduce at a fast rate
How does Antibiotic resistant bacteria occur?
- Antibiotic is added to a colony of bacteria of a non resistant strain
- However some individual, resistant bacteria survive and reproduce, increasing population of resistant bacteria
- The new colony is treated with a different antibiotic
- individual strains survive again and repopulate
- cycle repeats
What can Antibiotic resistant bacteria do if there is no preventative method?
If antibiotics are no longer active against the resistant strain of pathogen
- the new strain spreads rapidly as no one is immune + no effective treatment
How can more resistant strains of bacteria appearing be prevented?
- Not overusing antibiotics-> not used for non-serious infections (mild throat or ear infections) or viral infections (antibiotics don’t work)
- Finish course of medication every time-> ensures all bacteria is killed, therefore no mutations or resistant strains
- Restrict agricultural use-> prevent spread of antibiotic resistance from animal to human pathogens
What is MRSA?
Methicillin-resistant staphylococcus aureus
- bacteria that spread easily in hospitals, where they can become resistant very easily
What are measures taken to reduce the spread of microorganisms?
- Antibiotics should only be used when needed
- specific bacteria should be treated with specific antibiotics
- medical staff should wash their hands with soap and water between patient visits and wear disposable/regularly sterilised clothing
- Hospitals should have a high standard of hygiene to be really clean
- Patients infected with antibiotic resistant bacteria should be isolated from other patients
- Visitors to hospitals and care homes should wash their hands when entering and leaving
What happens when strains of bacteria are resistant to even the strongest antibiotics?
- nothing more antibiotics can do, patient may die
- scientists looks for new antibiotics-> hard to find a chemical that kills bacteria without harming human cells
- development of new antibiotics is costly and slow-> unlikely to keep up with emergence of new strains
What is Classification?
The organisation of living things into groups according to similarities
Why do scientists use classification?
- makes it easier to study organisms
- helps to understand how different groups are related to one another
- helps recognise biodiversity
Who is Carl Linnaeus? + What concept did he develop?
18th century, Swedish botanist
- grouped organisms depending on structure and characteristics
- made careful observations and used hierarchical structure to organise them
-Kingdom, Phylum, Class, Order, Family, Genus, Species
What is the pnemonic for the classification system?
Keep
Penis
Clean
Or
Forgo
Great
Sex
What Kingdoms did Linnaeus suggest?
Animal and Plant
- number of known living things was much less than today, so he suggested less kingdoms
Why has the model of classification been able to change?
Due to developments in microscopes, enabling scientists to compare internal structures of cells and organisms
What is a species?
A group of organisms that can breed together and produce fertile offspring
-The smallest group of clearly identified living organisms in Linnaeus’ classification system
How are organisms universally names?
By the binomial system of genus and species
What is the importance of the binomial naming system?
- language of scholars globally
- no one was offended their language wasn’t chosen
- most people could understand the names even though Latin was no longer spoken
What is the largest group under the Linnaean system of classification?
Kingdom
What is the newer, higher level of classification (above kingdoms? + Why was it created?
Domain
- understanding of internal processes and biochemical makeup of cells has increased recently
- many more species are known and recognised
How many Domains and Kingdoms are there?
3 domains-> 6 kingdoms
What is the Archaea domain?
Primitive forms of bacteria that include extremophiles (organisms that can live in extreme conditions)
1 Kingdom- archaebacteria
What is the Bacteria domain?
The true bacteria and the cyanobacteria, bacteria-like organisms that can photosynthesise
1 Kingdom- eubacteria
What is the Eukaryota domain?
Organisms that all have cells that contain a nucleus enclosing genetic material
4 Kingdoms- protista, fungi, plants, animals
What is the main way to identify organisms in the field?
relying on careful observation of organisms to decide their species
What are evolutionary trees?
Models that scientists use classification to show how they think different organisms are related, looking at similarities and differences between different groups of organisms
What do evolutionary trees allow us to do?
suggest relationships between different organisms
