Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Natural selection

Topic 5
...
2

Biology SL

To adapt or not to adapt?
➢ The vast majority of adaptations referred to in evolution and natural selection are
unconscious adaptation made by populations
➢ An organism that has characteristics that are well adapted for its environment is
said to be fit
➢ Natural selection tends to eliminate from a population individuals that show low
fitness
○

With some exceptions, organisms are incapable of changing themselves to
adapt

Many offsprings
➢ Many organisms produce more offsprings than what the environment can support
or could survive
○

Hundreds of eggs in fish

○

Thousands of seeds from trees

○

Millions of spores from mushrooms

➢ Only a few will survive to adulthood
➢ This is a method for these organisms to maximize the chances of some offsprings
to survive

➢ Struggle for survival is the competition for water, space, nutrients and sunlight in
order to stay alive
Adaptation and survival
➢ Which individuals survive and which ones don’t isn’t based on chance alone, but
it’s determined by their surroundings and the compatibility of their characteristics
with those surroundings
➢ Steps of evolution:
○

Overproduction and variety

○

Individuals with genetic characteristics that are poorly adapted for their
environment have less chances of survival

○

Well adapted individuals are more likely to survive

○

Successful individuals reproduce and genes are passed on

○

The gene pool changes over the years resulting in evolution

2

Natural selection

Topic 5

---