Transcript Diversity Adaptation_1

Diversity, Adaptation and
Change in Ecosystems
Sources of Variation
• Mutations – are random changes in the DNA
sequence of a chromosome. Mutations may be:
– neutral – have no effect on an individual
– harmful – hinder survival or reproductive success
(selected against and may disappear)
– beneficial – improve survival or reproductive success
(selected for and accumulate)
• Example: Bacteria mutating to become resistant to
drugs like antibiotics.
– Most biological diversity in organisms is due to
mutations
• Sexual Reproduction – involves the
production of an organism from two different
parents. The offspring inherits ½ the genetic
characteristics of both parents, increasing
variability.
• Asexual Reproduction – involves the
•
production of an individual from one parent.
The offspring is genetically identical to the
parent.
Example: Cloning
– Cloning decreases genetic diversity/variation
and could possibly cause an unstable
population.
Selective Advantage?
Evolution
The theory that changes
occur and can been seen in
the inherited traits of a
population from 1
generation to another
Evidence of Evolution
Paleontology (the study of fossils) has provided
scientists with an historical record of organisms
that once lived.
Biogeography -
• 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
Biochemical Evidence
• Scientists believe that the amino acid
sequences in proteins or related organisms are
more similar than those in unrelated organisms.
DNA sequences that make up different genes
control the traits an organism will have. More
similar organisms will have more similar DNA.
– Ex. Monkeys and humans share about 94% of the
same genetic information and about 90% of the same
amino acids.
• Other examples are: waste products
(nitrogenous waste), hormones, chromosomes
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).
• Theory of gradualism –speciation takes
place very slowly. Due to Natural selection
• Theory of punctuated equilibrium –
species evolve in bursts very rapidly,
followed by longer periods of stability
(little change). Again, due to natural
selection
• Divergent evolution – the evolution
into many different species.
– Due to different environmental
pressures
– Usually due to a barrier:
• Physical: island
formation/wall/mountain/etc
• Biological:pheromones/enemies
• Convergent evolution – the
development of similar appearance,
structure or behaviors in unrelated
species due to similar environmental
pressures.