Transcript Diversity Adaptation

Diversity, Adaptation and
Change in Ecosystems
Selective Advantage?
Evolution
The theory that changes
occur and can been seen in
the inherited traits of a
population from 1
generation to another
• Anatomical Evidence - Scientists can
study similarities and differences in the
anatomy of organisms and in their
embryological development to determine
ancestral links between organisms.
Homologous structures
- features with similar
structures, and different
functions that indicate an
evolutionary relationship
between organisms.
- Shows evolution from a
common ancestor
Ex. bat wing and human
hand
Ex. dolphin flipper and
forelimb of a dog
Analogous structures
– features with similar
functions, but very
different structures
that indicate there is
little evolutionary link
between organisms.
-Shows no common
ancestor
Ex. bat wing and
butterfly wing
Theories of Evolution
Lamarck –Inheritance of Acquired
Characteristics
• Lamark believed that organisms would
desire to evolve and develop a certain
trait that they required within a life
time to survive and would lose unnecessary traits (‘Use-Disuse’ Theory).
He also suggested that these traits
could be passed down to offspring
(Inheritance).
Ex. if a giraffe needed along neck to
reach food, the long neck would
evolve as the giraffes spent many
generations reaching for food.
Giraffe Evolution
Darwin – Natural Selection,
Survival of the Fittest
• Darwin believed that there were many
variations among organisms. Traits that
were better adapted to survival and
reproductive success, would be passed
down to future generations (Inheritance).
Darwin’s theory required that:
Darwin’s theory required that:
1. Variations exist among organisms.
2. In a changing environment, specific
variations were better adapted to
survival than others.
3. Only those organisms that survive (and
have the adaptive traits) will sexually
reproduce. ‘Survival of the Fittest’
4. The adaptive traits will be passed down
to the offspring.
5. **Natural Selection always occurs,
each trait has a chance to be passed on,
but its likely the better trait would be
passed
Speciation and Evolution
• Speciation is the formation of a new species. It can
occur by a step by step process known as allopatric
speciation.
1. A physical barrier separates a population into two
isolated groups.
2. Environmental pressures on the two groups are
very different causing the populations to evolve
independently.
3. Over time the accumulated differences between
populations become so extreme, the populations can no
longer interbreed to produce fertile offspring.
(They are two different species).
• Divergent evolution – the evolution
into many different species.
– Due to different environmental
pressures
– Usually due to a barrier:
• Food source
• Convergent evolution – the
development of similar appearance,
structure or behaviors in unrelated
species due to similar environmental
pressures.