Inheritance, Variation, Evolution- Flashcards
State Charles Darwin’s 3 key observations
Individual organisms within a particular species show a wide range of variation for a characteristic
Individuals with characteristics most suited to the environment are more likely to survive to breed successfully
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
Variation within a population exists
Some individuals are more suited to their environment (due to the characteristics they possess)
The individuals who are more suited to the environment are more successful
These individuals are more likely to survive and breed
These individuals will pass on the alleles for the beneficial characteristics to offspring
after MANY generations the beneficial alleles will become more common in the population
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
theory challenged the idea that God made all the animals and plants that live on Earth
insufficient evidence at the time the theory was published to convince many scientists
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
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
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
Explain why Lamarck’s hypothesis was rejected
Experiments did not support his proposal
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’
- the development of a new species
- it occurs when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
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)
A population of one species shows variation between individuals
The population becomes separated by a geographical barrier e.g. mountain range
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
In each group there is variation in the characteristics beneficial characteristics to the their offspring
Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
Over time the variants in the two groups change so that they can no longer breed with each other to form fertile offspring
The groups are now defined as two separate species
Define the term ‘extinction’
Extinctions occur when there are no remaining individuals of a species still alive
Give 5 reasons why extinction may occur
Significant environmental change e.g. destruction of their habitat
A new disease
A new predator e.g. humans hunting and killing them
Individuals fail to compete against successfully against a new species for food
A catastrophic event e.g. volcanic eruption
Name the Scientist who made major discoveries in genetics
Gregor Mendel
Describe the work of Gregor Mendel
carried out breeding experiments on plants.
State the 2 main sources of evidence for the theory of natural selection
Fossils
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
Gradual replacement by minerals
casts and impressions
preservation in areas where no decay occurs
Explain how gradual replacement by minerals forms a fossil
Hard materials such as booth, shells, teeth etc do not decay easily even when they are buried
These substances are slowly replaced by minerals- forming rock-like substance shaped like original hard part
The surrounding sediments are compressed to form sedimentary rock
The fossil remains as a distinct shape within the sedimentary rock
Explain how fossils form from casts and impressions
An organism is buried in soft material e.g. clay
The clay hardens around the organism
The organism decays inside the hardened clay
This forms a cast around the organism
Casts can also form around animal’s burrows or plant’s roots
Footprints can also be pressed into clay and leave an impression when the clay hardens
Explain how preservation can occur in areas where no decay occurs
Amber and tar pits have no oxygen or moisture so no decay occurs in these areas
Glaciers are too cold for decay to occur
Peat bogs are too acidic for decay to occur
Explain why Scientists can’t be sure how life began
The fossil record is incomplete
It is not possible to regenerate the conditions that existed when life began so no experiments can be carried out
This means there is a lack of valid and reliable evidence
Why is the fossil record incomplete
Some organisms are soft-bodied and fully decay leaving no fossil
Not all fossils have been found yet
Some organisms die in areas where fossils do not form e.g. centre of a forest
Some fossils have been destroyed e.g. geological activity
