B15 Flashcards
Genetics and evolution
1
Q
Who was Gregor Mandel ?
A
- father of modern genetics
- Austrian monk in mid-late 1800s
- conducted breeding experiments with different breeds of peas
[] first had yellow peas, then crossed with green peas
[] all offspring were yellow
[] when crossed the offspring with each other, one in four were green, whilst the others were yellow
[] Mandel suggested units of inheritance that were recessive and dominant; in this instance, the yellow colouring was the dominant allele over the green colouring
[] called monohybrid inheritance
2
Q
Why was Mendel’s work finally accepted 16 years after his death in 1884 ?
A
- scientists observed “dance of the chromosomes” during cell division for the first time under a microscope
[] was suggested that Mendel’s units of inheritance were carried on chromosomes - scientists peer reviewed his work, reproducing his experiments to replicate the results he achieved
[] gave Mendel credit when they published
3
Q
How was the structure of DNA discovered, leading to the discovery of gene function (explaining Mendel’s units of inheritance) ?
A
- one team in London; Wilkins and Rosalind Franklin
[] were attempting to look at the structure of DNA through using X-rays - one team in Cambridge; Crick and Watson
[] were attempting to build a 3D model of DNA to explain how it functions - Wilkins released Franklin’s x-rays without her permission to the other team, who were able to find DNA’s double helix structure using them
- sadly, Franklin died of cancer before the other three were given a Nobel for their works in genetics
- before long, gene theory, explaining Mendel’s units of inheritance, was come up with
4
Q
Describe Lamarck’s theory of inheritance/evolution
A
- all organisms evolved from primitive worms
- animals evolve through the use/disuse of certain characteristics
[] for example, if a giraffe stretched its neck a lot to reach higher leaves on trees, its offspring would inherit a longer neck, and this would continue over many generations until giraffes with long necks were the norm
[] alternatively, if an animal didn’t use a characteristic, such as humans having no use for tails, they would shrink over generations and eventually disappear
5
Q
What were the problems with Lamarck’s theory of evolution ?
A
- people weren’t fond of the idea of being descended from worms
- people could see that his theory wasn’t right; parents with big muscles didn’t pass these on to their children, neither did parents with dyed hair or broken or amputated limbs
- if the theory WAS true, certain characteristics would never stop growing bigger or more complex, leading to eventual evolutionary drawbacks instead of adavntages
[] also the lack of super-evolved animals is an indicator that this hasn’t happened - creationists
6
Q
Describe Darwin’s theory of evolution by natural selection
A
- more offspring than the environment can support are produced
- variation exists in the population due to random genetic mutations
- individuals in the population with random traits that allow them to survive better than others (such as longer necks in giraffes, or broader leaves in forest floor plants) are more likely to survive
- these individuals then breed and pass the beneficial trait onto their offspring
- this repeats over many generations until the new beneficial trait becomes the standard
7
Q
How did Darwin come up with and build up evidence to prove his theory of evolution by natural selection ?
A
- on ship where he was supposed to do geology mapping out the Galapagos islands, became intrigued by the many different species of the same animals
- observed the Galapagos finches in particular and how they lived in close proximity however had completely different traits based on where exactly they lived, what their main food sources were etc.
- when went home to England, conducted breeding experiments with pigeons to demonstrate how traits could be artificially selected and model how nature had done this with all animal species
- had wide network of fellow scientists and pigeon breeders with whom he talked, gathered evidence and asked for advice
- eventually pushed to publish in 1859 when realising Alfred Wallace had similar ideas and was readying to publish before him
8
Q
Give the main reasons why Darwin’s work was only accepted gradually in many places and not soon after publishing
A
- creationism and the importance of religion to early Victorian England
- some scientists thought there hadn’t been enough time to peer review and gain new supporting evidence and so were hesitant to accept his theory straight away
- no way to explain how variety and inheritance came about since gene theory wasn’t developed until 50 years after his death
[] since no explainable mechanism at the time, harder concept to grasp, understand and accept
9
Q
Who was Alfred Wallace ?
A
- scientist alive at the same time as Darwin, who almost beat Darwin to publish
[] published joint paper with Darwin in 1958, a year before On The Origin of Species was published
[] worked in mutual respect with Darwin for the rest of their lives - collected more evidence for natural selection throughout his lifetime
[] studied warning colouration in animals as well as how geographic location aided in forming species - known as the father of the modern understanding of speciation in animals
10
Q
What is speciation ?
A
When two populations of the same animal become so different via natural selection that they can no longer interbreed to produce fertile offspring
11
Q
Describe the process of speciation
A
- a population of an animal is split into two, isolated by a change in the environment
- conditions in their new locations may be different from their old locations, meaning different traits are advantageous than before
- variation exists in the populations
- animals in both populations evolve in different ways by natural selection, adapting to the new habitats/environments in different ways
- this happens over many generations
- eventually, the characteristics of the two populations will be so different that they cannot interbreed to produce fertile offspring any longer
12
Q
What are the two types of isolation that may lead to speciation ?
A
- geographical isolation
[] isolation via the formation of a new/different geographical feature, like a new mountain range, river or the formation of new islands via earthquakes or eruptions - environmental isolation
[] isolation via partial change of climate, affecting only one or two parts of the entire population
13
Q
What is a fossil ?
A
preserved remains of organisms from millions of years ago - found in ice, rock etc.
14
Q
Describe the main ways in which fossils are formed and which types of fossils they produce
A
- one or more conditions for decay are not met (eg. no oxygen, temperature is too low, too little moisture), so the organism is pretty much wholly preserved
[] these fossils are rare but extremely useful
[] scientists can see almost exactly what the organism looked like in life, and can extract DNA from the fossil to compare it to modern day animals - harder parts of the animal/plant replaced by minerals over millions of years
- mould fossil = animal/plant leaves imprint in mud, which then becomes fossilised
[] often found in rock - cast fossil = mould fossil is formed then filled in (original mud may not be fossilised by this stage)
[] often found in rock
[] these can also fossilise footprints, droppings and other traces of the animal/plant; useful for scientists to build up an image of the animal’s diet, life on ancient earth etc.
15
Q
Describe how an organism is fossilised
A
- organism dies
- (if conditions for decay are met) the flesh/organic material rots, leaving only the skeleton/hard parts of the organism
- these remains are covered in sand and mud before they can be damaged
- protected by the layers of earth and sand above it, the fossil is mineralised and turns to rock
- rocks shift around with the fossil between them
- fossil emerges as a result of erosion of the rock above it
16
Q
What are the limitations of fossils in terms of informing scientists about early life on Earth ?
A
- many of the very earliest organisms were soft bodied, so couldn’t fossilise well/at all
- fossils are rare; conditions for fossilisation are hard to meet and this means that fossils are more common in certain areas than others, missing out information from early life in those other places
- there are still many undiscovered fossils
17
Q
How do scientists use fossil records to evaluate evolution ?
A
- most fossil records are largely incomplete, and so evolution of the animal cannot be accurately studied
- some fossil records, like those for horses, sharks etc. are much more fully completed
[] using these, scientists can see which changes were the most prominent in the organism, if any, and what the climate and ecology of the prehistoric world looked like
[] can see that some animals, like sharks, have evolved very little over millions of years, as they evolved into a beneficial state early on and there were no CHANGES IN THE ENVIRONMENT, so no further natural selection/evolution needed to occur
18
Q
What is extinction ?
A
The permanent loss of all members of a species
19
Q
Why do certain species go extinct ?
A
- over time, the environment/conditions of the animal’s habitat changes
- once beneficial characteristics are no longer useful and another species is favoured
- the old species is now outcompeted for food, space and resources and so dies out
- some species that have gone extinct have living relatives, whilst others are completely lost to the world
20
Q
Describe the main ways in which organisms can cause extinction
A
- new disease mutates/introduced to an environment
[] the species in that environment did not evolve to have resistance towards that disease and cannot cope with the change, so the disease wipes out the whole population
[] most common in close quarters, like on islands or in cages of farm animals - new predators evolving/being introduced to the environment
[] have new adaptations and characteristics that the prey species in an area are not used to and thus are defenceless against; the predator species may then kill off all members of the prey species faster than it can breed, thus making it extinct - successful competition
[] introduction of a more successful species to an area where the native species are outcompeted and extincted by the new
[] evolution by natural selection providing such advantageous traits that the other competitors are outcompeted for resources and thus die out
21
Q
What is geological time ?
A
Time periods of earth based on rocks
examples:
- cretaceous period
- neolithic period
- ice ages
22
Q
What is mass extinction ?
A
When most species of life on earth die out due to a significant change to the climate/environment (like an Ice Age, a single catastrophic event like a massive asteroid (what killed the dinosaurs) or periods of intense global warming)
[] usually don’t last more than a few million years (short time relatively to other geological time periods)
23
Q
Describe the two main theories as to the reason for the most recent mass extinction (around 65 million years ago)
A
- theory 1:
[] massive asteroid crashed into earth in Mexico, causing tsunamis, earthquakes and other natural disasters that killed the dinosaurs
[] dust and debris from the impact floated in the air and caused an ice age, blocking out the sun and disallowing photosynthesis for plants, killing many
[] there is a large crater in Mexico (180km)
[] lots of iridium found there (that mineral only forms when a rock is hit with massive amounts of force)
[] there has been lots of crater debris found near the crater site, thinning as you move away - theory 2:
[] process of extinction was much more gradual, starting over 100 million years ago
[] global warming triggered sea ice melting and a rise in sea levels
[] the sudden drop in sea temperatures caused mass extinction
[] scientists found unexpected mineral changes in fossils from Norway
24
Q
Describe how bacteria develop resistance to antibiotics through natural selection
A
- variation exists in a bacteria colony due to random mutations in DNA during the process of binary fission
- antibiotic A, when applied kills 95% of the bacteria
[] these 5% survive due to random genetic mutations that allowed them to be unaffected by the antibiotic (resistance) - these resistant bacteria multiply until there is a new colony
[] the entirety of the new colony is resistant to antibiotic A now - this repeats over many times, with colonies further and further along having more and more resistance to a wide range of antibiotics
25
Q
Why can bacteria evolve quickly ?
A
reproduce very quickly, so natural selection is sped up
26
Q
Describe the main ways in which to prevent/reduce the evolution of antibiotic resistant strains of bacteria
A
- don’t overuse antibiotics
[] antibiotics not prescribed for viral infections, as have no effect on viruses
[] not prescribed for milder bacterial infections like throat or ear infections - finish full course of prescribed antibiotics
[] kills ALL harmful bacteria and prevents development of resistant strains - limit agricultural use of human antibiotics
[] high agricultural use to either prevent infection or promote growth can create superbacteria resistant to many antibiotics, which, when eaten by humans, are very dangerous and hard to treat
27
Q
Why are bacteria with high levels of resistance to a wide range of antibiotics dangerous ?
A
- harder to treat, so fatality rates of the disease rise until a new drug is found to treat the disease
- can evolve into resistant forms faster than humans can make new antibiotics to kill these bacteria (production is expensive, slow and it is hard to find (organic) chemicals that actually work as antibiotics)
28
Q
What is MRSA ?
A
- Methicillin Resistant Staphylococcus Aureus
[] bacterium resistant to many kinds of antibiotic - found in hospitals and care homes, as use of antibiotics in these places are perfect for building resistance, then travelling to humans and spreading through the doctors and nurses who work between patients
29
Q
How was the spread of MRSA reduced ?
A
- not prescribing/using antibiotics before they are needed
- use of specific antibiotics for specific bacteria
- doctors/nurses washing hands or using hand sanitiser between patients
[] also wear disposable clothing (scrubs) or clothing that can easily be sterilised - visitors should wash their hands when they enter and leave
- hospitals and care homes to have high standards of hygiene
- patients infected with antibiotic-resistant bacteria to be looked after in isolation to other patients
30
Q
What is classification and why is it important ?
A
Organisation of organisms into groups according to their similarities
[] allows to understand ecological and evolutionary relationships between organisms
[] makes organisms easier to study
[] enables to recognise biodiversity present
[] gives scientists a common language to discuss biodiversity/organisms and their characteristics in
31
Q
How did Linnaeus (the first person to classify) classify organisms ?
A
- natural classification system
[] kingdom
[] phylum
[] class
[] order
[] family
[] genus
[] species
32
Q
How do you write organism names in the binomial (two name) system put forward by Linnaeus ?
A
- Latin
- first name is the name of the organism’s genus with a capital first letter
- second name is the organism’s species in all lowercase
- the names are underlined when written by hand, or in italics when printed
33
Q
Which were the first two kingdoms suggested by Carl Linnaeus and how were they divided ?
A
- animal
[] move whole bodies by themselves
[] do not have cellulose cell walls - plant
[] do not move entire bodies around
[] have cellulose cell walls
34
Q
What are the kingdoms in the modern classification system based on Linnaeus, and why do they differ so much from the original two ?
A
- plants, animals, protista, fungi, prokaryotes
- in the modern world, much more is known about the biochemistry of organisms, as well as the discovery of new types of organisms thanks to developments in technology
35
Q
In the Woeseian classification system, what are the different levels of classification, and why was the new level put forward by Woese ?
A
- system:
[] domain
[] kingdom
[] phylum
[] order
[] family
[] genus
[] species - domains put forward due to the analysis of the biochemistry of cell ribosomes and the differences in cell reproduction across organisms
- 3 domains:
[] archaea
(primitive forms of bacteria, including extremophiles - 1 kingdom under this domain; archaebacteria)
[] eukaryota
(all have cells with a nucleus that encloses their genetic material - 4 eukaryotic kingdoms; plants, animals, protista and fungi
[] bacteria
(contain the true bacteria and cyanobacteria (bacteria-like organisms which can photosynthesise) - contains 1 kingdom; eubacteria)
36
Q
What is an evolutionary tree ?
A
- scientific model allowing to suggest and demonstrate different paths of evolution for a certain species of organism
[] allows to suggest relationships between organisms too - built up by looking at the similarities and differences between organisms
[] similarities and differences found through:
. careful observation of the organisms in the field (such as habitat, colouration, specific physical characteristics, diet, mannerisms, life etc.)
. biochemical analysis of similarities and differences in DNA
. (for fossils) fossil data analysed and compared
