Paper 2: Topic 6 Inheritance, variation & evolution - Development of understanding of genetics & evolution Flashcards Preview

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Flashcards in Paper 2: Topic 6 Inheritance, variation & evolution - Development of understanding of genetics & evolution Deck (34)
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What evidence did Charles Darwin use propose his theory of ‘survival of the fittest’?

  1. Fossils
  2. Geology
  3. Animal behaviour
  4. Observational studies of some species
  5. Discussion with other Scientists


State Charles Darwin’s 3 key observations

  1. Individual organisms within a particular species show a wide range of variation for a characteristic
  2. Individuals with characteristics most suited to the environment are more likely to survive to breed successfully
  3. The characteristics that have enabled these individuals to survive are then passed on to the next generation


Explain Charles Darwin’s concept of ‘survival of the fittest’ Hint: 7 key steps

  1. Variation within a population exists
  2. Some individuals are more suited to their environment (due to the characteristics they possess)
  3. The individuals who are more suited to the environment are more successful
  4. These individuals are more likely to survive and breed
  5. These individuals will pass on the alleles for the beneficial characteristics to the their offspring
  6. Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
  7. Over time the characteristics of the population change – this means it has evolved


Give 3 reasons why Charles Darwin’s theory was not fully accepted at the time

  1. The theory challenged the idea that God made all the animals and plants that live on Earth
  2. There was insufficient evidence at the time the theory was published to convince many scientists
  3. The mechanism of inheritance and variation was not known until 50 years after the theory was published


Name a Scientist, other than Charles Darwin, who put forward an alternative hypothesis for evolution

Jean-Baptiste Lamark


Describe Lamarck’s hypothesis for evolution

  • He proposed that changes that occur in an organism during its lifetime can be inherited
  • He suggested in an organism used a characteristic a lot then it would become more developed in its life time
  • He suggested offspring would then inherit these acquired characteristics from their parents

Remember: We now know that in the vast majority of cases this type of inheritance cannot occur


Give an example of Lamarck’s theory of acquired characteristics

Example 1

  • A giraffe stretches their neck to reach the leaves on a higher tree
  • The neck would get longer during the giraffe’s lifetime
  • The giraffe’s offspring would then inherit the longer neck

Example 2

  • A rabbit uses its legs a lot to run away from predators
  • The rabbit’s legs would get longer during its lifetime
  • The rabbit’s offspring would then inherit the longer legs


Explain why Lamarck’s hypothesis was rejected

  • Experiments did not support his proposal
  • E.g. colouring the fur of a rabbit does not result in the rabbit having babies with a different colour fur


Explain why over time Darwin’s hypothesis was accepted

  • The study of genetics supported his hypothesis
  • Other evidence was also found in fossils
  • Recent discoveries of the evolution of antibiotic resistance in bacteria by natural selection have also provided more proof


Explain when a hypothesis becomes a theory

When there have been sufficient investigations and experiments into the hypothesis that have generated data & evidence to support the hypothesis


Describe the work of Alfred Russel Wallace

  • Alfred Russel Wallace independently proposed the theory of evolution by natural selection
  • He published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year
  • Wallace worked worldwide gathering evidence for evolutionary theory
  • He is best known for his work on warning colouration in animals and his theory of speciation
  • Alfred Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation


Give an example of the work carried out by Alfred Russell Wallace

  • He studied warning colours in butterflies that were used to deter predators from eating them
  • He proposed that the warning colours were a beneficial characteristic that had evolved by natural selection


According to the theory of evolution where did all life originate from?

Simple life forms that first developed more than 3 billion years ago


Define the term ‘species’

  • A group of similar organisms that can interbreed to produce fertile offspring
  • They share a common ancestor and have similar characteristics


Define the term ‘speciation’

When a single population of one species evolves so that different phenotypes can no longer interbreed with each other to form fertile offspring In summary – it is the development of a new species


Describe what may cause speciation may occur

A population becomes separated due to a geographical barrier e.g. ocean, mountain range


Explain the process of speciation (i.e. how speciation occurs)

  1. A population of one species shows variation between individuals
  2. The population becomes separated by a geographical barrier e.g. mountain range
  3. The 2 different groups experience different environmental conditions in their respective habitats e.g. one side of the mountain range has a warmer climate than the other side
  4. In each group there is variation in the characteristics beneficial characteristics to the their offspring
  5. Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
  6. Over time the variants in the two groups change so that they can no longer breed with each other to form fertile offspring
  7. The groups are now defined as two separate species


Who was the pioneer scientist of the theory of speciation?

Alfred Russell Wallace


Define the term ‘extinction’

Extinctions occur when there are no remaining individuals of a species still alive


Give 5 reasons why extinction may occur

  1. Significant environmental change e.g. destruction of their habitat
  2. A new disease
  3. A new predator e.g. humans hunting and killing them
  4. Individuals fail to compete against successfully against a new species for food
  5. A catastrophic event e.g. volcanic eruption


Name the Scientist who made major discoveries in genetics

Gregor Mendel


Describe the work of Gregor Mendel

In the mid-19th Century Gregor Mendel carried out breeding experiments on plants.


State Mendel’s main observation from his studies on plants

The inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged


State Mendel’s 3 main conclusions that he drew from his studies on plants

  1. Characteristics in plants are determined by hereditary units
  2. Hereditary units are passed on unchanged from parents to offspring (one hereditary unit is passed from each parent)
  3. Hereditary units are either dominant or recessive – if both types of units are present the dominant unit will be expressed


Give 3 reasons why it took time for people to accept and understand Mendel’s work

  1. Mendel’s work was new and innovative – there was no similar work being undertaken and Scientists did not know about DNA or genes
  2. His work was only appreciated after his death
  3. It was only with the observations of many Scientists who used Mendel’s work as a starting point that we began to understand about genes


Give 3 key dates in the history of the understanding of genes and DNA

  • Late 1800s = scientists could observe and study the behaviour of chromosomes during cell division
  • Early 20th Century = The concept (idea) of units of hereditary being located on chromosomes was suggested. This led to the idea that the ‘units’, now called genes, were located on chromosomes.
  • 1953 = Structure of DNA was determined and the mechanism for gene action was worked out This scientific work by many scientists led to the gene theory being developed


State the 2 main sources of evidence for the theory of natural selection

  1. Fossils
  2. Antibiotic resistance in bacteria


Define the term ‘fossil’

The preserved remains of organisms that live many thousands of years ago found in sedimentary rock


State the 3 ways in which fossils can form

  1. Gradual replacement by minerals
  2. From casts and impressions
  3. From preservation in areas where no decay occurs


Explain how gradual replacement by minerals forms a fossil

  1. Hard materials such as booth, shells, teeth etc do not decay easily even when they are buried
  2. These substances are slowly replaced by minerals
  3. The layers of minerals builds up over the original part
  4. The surrounding sediments are compressed to form sedimentary rock
  5. The fossil remains as a distinct shape within the sedimentary rock

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