Evolution Flashcards
How long ago was the big bang?
13.7 billion years
How long ago was the sun formed?
5.6 billion years ago
How long ago was the Earth formed?
4.6 billion years ago
How long ago was the first life?
3.6 billion years ago
Can we know for sure how and when life on Earth began? Why?
no
no-one was there to observe it
we cannot do experiments to repeat the origin of life
What was Lamarck’s theory?
The inheritance of aquired characteristics
What does Lamarck’s theory say?
characteristics of individuals change during their own lifetime
the changed (aquired) characteristics are passed on to the next generation
Use the example of long necks for giraffes to explain Lamarck’s theory
giraffes used to have short necks, but they preffered to eat leaves from high trees
as they reached for high trees their necks became longer
the long neck characteristic was passed on to offspring
What are the pros of Lamarck’s theory?
changes in individuals can be aquired over time
What are the cons of Lamarck’s theory?
aquired characteristics are not passed on
What was Darwin’s theory?
Theory of evolution by natural selection
What was Darwin’s observations on finches?
there is a lot of variation between species
different islands have different food sources
different beaks suit different food sources
What were Darwin’s conclusions?
finches show variation in beak size and shape
finches with long, thin beaks are better adapted to catch insects living between rocks, compared to finches with wide, short breaks
finches with long, thin beaks are more likely to survive and breed while less well adapted finches may die before reproducing
the characteristics of the finches with long, thin beaks are passed on to the offspring
over time the number of finches with long, thin beaks increases, while the number of finches with short, wide beaks decreases
What is natural selection
mechanism for evolution
explains how some characteristics become more common
What does natural selection show about selection pressures?
selection pressures exist in environment (e.g. food source)
this leads to selection (survival) of those organisms that are best suited to this particular environment
these survive and pass on their genes (while others don’t)
characteristics of these organisms become more common
What are some examples of selection pressures?
predators
food
disease
climate
finding a mate
where does variation come from?
random mutations in genes
not forced by the environment
variation exists before selective pressures (but can be useful later)
Complete this beetle example diagram


what are peppered moths?
there are dark and light forms of the peppered moth
moths rest on tree bark during the day
before the industrial revolution what was the case with tree bark and peppered moths?
tree bark was covered with lichen (makes bark pale)
predomincance of light forms of moth in UK
after the industrial revolution what was the case with tree bark and peppered moths?
dark forms in polluted areas (light forms in rural areas)
Complete this table about peppered moths


Complete this table about antibiotic resistant bacteria


Complete this table about sickle cell anaemia

