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
why is it better to be a carrier of sickle cell anaemia in regions with malaria than not to be?
if you are a carrier then you cannot have sickle cell anaemia
thus you are protected
what is the definition of Darwin’s Theory of Evolution?
all species of living things have evolved from simple life-forms which first developed more than three billion years ago through the process of natural selection
what is the variation, selection pressure and organisms selected for for rabbits with very long ears in the desert?
variation = different ear length
selection = hot temperature
organisms selected for = long ears - larger SA/V ratio, easier to lose heat
what is the variation, selection pressure and organisms selected for stick insects?
variation = different colours/shape of insect
selection pressure = predators
organisms selected for = good camouflage - harder for predator to find them
what is the variation, selection pressure and organisms selected for giraffes having long necks?
variation = different neck length
selection pressure = food - high up and mates
organisms selected for = long necks -able to reach food, attractive
what is the variation, selection pressure and organisms selected for cacti having spines instead of leaves?
variation = different sized spines/ leaves
selection pressure = heat (water loss), herbivores
organisms selected for = smaller SA and least water is lost, protection from predators
what is the variation, selection pressure and organisms selected for peacocks having brighlty coloured feathers?
variation = different feather colours
selection pressure = finding a mate (sexual selection)
organisms selected for = most brightly coloured feathers - most attractive
what is a fossil?
mineralised or otherwise preserved remians of organisms
what two categories of fossils are there?
body fossils
trace fossils
what is a body fossil?
fossilised remains of an organism