GCSE BIology - B15 - The History of Genetics

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What experiment did Mendel complete?
He cross-bread smooth peas, wrinkled peas, green peas and yellow peas and counted the different offspring. he found that some of the characteristcs were inherited in clear and predictable patterns..
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What did Mendel suggest about genetics?
That there were seperate units of inherited material and some characteristics were dominant over others and that they never mixed together. He published his findings in 1866.
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Why did people not acept Mendel's theory?
AS at the time, no one knew about genes or chromosomes so people didn't understand his theories.
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When did people finally begin to accept Mednel's theory?
In 1884, 16 years after his death as people could now see chromosomes through a microscope.
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What did Maurice Watkins and Rosalind Franklin doconcerning inheritance?
They looked at the structure of DNA using X-rays.
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How did James Watson and Francis Crick come up with the structure of DNA as being a double helix?
The were trying to build a 3D model of Dna that would explain how it works and used Rosalimd Franklin's X-ray results which were released by Maurice Wilkins without Franklin's permission.
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What is Lamarck's theory of evolution?
Thought animals adapted and evolved to suit their environment, every type of animal evolved from worms, any useful changes would be passed on from parent to offspring.
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What were the problems with Lamarck's theory of evolution?
No evidence for his 'foundation of life' and people did not like the idea of being descended from worms. They could see that changes from their body e.g. big muscles were not passed on to their children.
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What did Darwin discover in South America?
A new form of the common rhea.
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What did Darwin discover on the Galapagos Islands?
Species varied from island to island, finches were very similar on different islands yet each was adapted to make the most of local conditions. He collected huge numbers of speciments of animals and plants and dd detailed drawings and written notes.
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What are the main ideas in Darwin's theory of evolution?
Reproduction alwasy gives more offspirng than the environment can support, when animals breed they pass on useful characteristics that have allowed them to survive to the next generation and variation in each characteristc within a species.
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What evidence did Darwin have?
Used plants and animals, noting that organisms on different islands had adapted to their environmet by natural selection. He also bred pigeons to show how features could be artificially selected and studied different types of barnacles.
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Why was Darwin's theory of evolution not immediately accepted?
Challenged religious beliefs, many scientists felt there was not enough evidence and hard for people to underatsnd as how inheritance happened was not explained until 50 years after Darwin published his book.
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What theory did Alfred Russel Wallace come up with?
That if a species existed in various forms, those which were poorly adapted to change were likely to die out, leaving onky the well adapted to survive and breed. He sent these ideas in a letter to Darwin.
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What evidence did Alfred Russel Wallace have concerning inheritance?
Warning colouration in animals and cklear theories on the role of geographic isolation in the formation of species.
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What is genetic variation?
The wide range of allelees controlling a population's characteristics, resulting in mutation and sexual reproduction.
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What is natural selection?
The alleles that are slected will control characteristics that help the organism to survive and breed successfully.
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What is speciation?
Isolation between species, alleles selected that allow organisms o breed and survive succesfully in new conditions are slected, genetic variation between populations increase, eventually characteristcs change so much that they can't inter-breed.
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What is geographical isolation?
Two populations become physically seperated, e.g. by a new rriver r mountain range. This often leads to speciation.
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What is environmental isolation?
When climate changes in one area which an organism lives but not in other areas, e.g. plants will flower at different times a year if the climate is warmer in one area. This causes breeding times to change and new species to eventually emerge.
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How are fossils formed from decay?
When there is little/no oxygen present or temp is too low and a plant/animal doesn't decay after death. They are presevered in ice/peat. Rare, but tell us what an animal looked like.
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What evidence do decayed fossils give us?
What a animal has been eating or the colour of a flower, Scientists can extract the DNA and compare it to organisms today.
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Give another example of fossil evidence:
Preserved traces which animals or plants have left behind e.g. fossil footprints, burrows, droppings.
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How are mould fossils formed?
When harder parts of animals/plants are replaced by minerals as they decay and become part of the rock. Mould fossils form when an impression of an organism is made in the mud and becomes fossilised.
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How are cast fossils formed?
When a mould is filled in.
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Why is the fossil record incomplete?
Many early life forms were sof-bodied organisms, right conditions for fossil formation are rare and there are many fossils still to be foun.
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Why os the fossil record useful?
Helps scientists to undertand how much organisms have changed since life developed on earth.
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What is extinction?
The permenant loss of all the members of a species.
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Why does extinction occur?
As conditions change, new species evolve that are better suited to survive the new condition. The old species start to die out because they can't cope with the changes and gradually die out as they can' compete so well for food.
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Give examples of changes in the environment that cause extinction:
Temperature, new predators, new diseases, new, more successful competitors.
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How can new predators cause exitnction?
If the prey animals animals do not have the adaptations to avoid them, tey can be wiped out rapidly. New predators may evolve or move into the new territory and this can be done by human intervention.
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How can new diseases cause extinction?
Most likely to cause extinction on silands, where the whole populaton of the plant or animal is closed together and so the disease can spread rapidly.
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How can successful competition cause extinction?
New mutations give one organism a huge advantage over another so the other speces finds it dfficult to compete for food and survive.
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What is geological time?
Changes that take place to the Earh over billons fo years.
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What is the main cause of extinction?
Climate change as many organisms aren't adapted to the new conditions and so cannot survive and breed.
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Gve examples of two signle catastrophic events that could cause mass extinction:
A huge volcanic eruption or the collision of giant asteroids with the Earth.
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What is the most common theory over what detsroyed the dinosaurs?
That around 65million years ago a giant asteroid collided with the Erath in Mexico,
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What evidence is there for an asteroid killing the dinosaur?
Crater in mexico and scientists also found lots of iridium deep below the crater and this is only formed when rock is hit with a massive force.
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Why would the asteroid colision have caused extinction?
As it would have caused huge fires, earthquakes, landslides and tsunamis. The dust in theatmosphere also made everywhere almost dark so plangs struggled to survive and the temp drop introduced a global winter.
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What is the global warming theory concerning extinction of the dinosaurs?
The melting sea ice flooded the seas and oceans with very cold water. The drop in sea temp triggered mass extinction.
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What evidence is there that global warming made the dinosaurs extinct?
An unexpected change in fossils and minerals found in areas of Norway.
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How does antibiotic resistant bacteria spread?
The individual resistsant bacteria can survive and reproduce, increaisng the population. The antibiotics are no longer active agaonst the pathogen so the new strain spreads rapidly,
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How can we prevent more resistant strains of bacteria from appearing?
By not overusing antibiotics/using them to treat a virus, by finishing the course of antibiotics (to make sure all the bacteria is killed) and by using less of antibiotics in agriculture as antibiotic resistance can spread from animals to humans.
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What is MRSA?
A type of bacteria that is resistant to several widely used antibiotics.
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What can be done to reduce the spread of MRSA?
Only take antibiotics when really necessary, treat specific bacteria with specific antibiotics and isolate patients infected away from other patients.
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What are doctors currently trialing as sources for antibiotics?
Crocodile blood, fish slime and soil samples.
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Why is it difficult to find antibiotics?
As it is hard to find chemicals that kill bacteria without damaging human cells.
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What is classification?
The organisation of living things into groups accoridng to their similarities.
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Who came up with the natural classification system?
Carl Linnaeus, he grouped organsms togetehr based on their structure and characteristcs. He classified organisms into kingdom, phylum, class, order, family, genus, species.
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What ae the six kindoms scientists we use today?
Arcaebacteria, eubacteria, protista, fungi, plants and animals.
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What is a species?
The smallest group of organisms, a species is a group of organisms that can breed together to produce fertile offspring.
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What are the rules for writing binomial scientific names?
Firts name, genus, capital letter, second name, species, lowercase letter, bth names must be underlines or written in italics.
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What is a domain?
A new, higher level of classification above kingdoms.
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What are the three domains we use today?
Archaea, bacteria and eukarota.
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What is the archaea domain?
These include extremeophiles and the domain contains the archaebacteria kingdom.
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What is the bacteria domain?
These are true bacteria and bacteria-like organisms that can photosynthesise. Ths domain contains the eubacteria kingdom.
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What is the eukaryota domain?
These organisms have cells that contain a nucleus enclosing the genetic material. This includes the protista, fung, plants and animals kingdoms.
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What is an evolutionary tree?
These allow scientists to suggest relationship as well as similarities and differences between organisms,.
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How do scientists decide which species an animal belongs to?
DNA evidence and they look for similarities and differences in the DNA to work out the evolutonary relationships between organisms
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How do scientists build up evolutionary trees for living and extinct organisms?
They use classification data for living animals and fossil data for extinct animals.
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Other cards in this set

Card 2

Front

What did Mendel suggest about genetics?

Back

That there were seperate units of inherited material and some characteristics were dominant over others and that they never mixed together. He published his findings in 1866.

Card 3

Front

Why did people not acept Mendel's theory?

Back

Preview of the front of card 3

Card 4

Front

When did people finally begin to accept Mednel's theory?

Back

Preview of the front of card 4

Card 5

Front

What did Maurice Watkins and Rosalind Franklin doconcerning inheritance?

Back

Preview of the front of card 5
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