What is evolution
Process of change in something, over
time
What is biological evolution
Process whereby populations change over time in response to changes in their environment
What is a belief
an explanation for a phenomenon that is based on religious or cultural values that cannot be proved or disproved
using scientific evidence.
What is a hypothesis
a possible explanation of a phenomenon, that can be tested using observations and / or experiments.
What is a theory
a widely held explanation of a phenomenon that is supported by numerous observations, experiments & scientific evidence.
Using combination of sources of info evolutionary scientists…
developed detailed histories of the evolution of life forms
* demonstrate the evolutionary relationships among
organisms that are currently alive
Fossils
- Paleontology is the study of fossils
- Fossils are the remains or traces of
organisms that once lived on earth
-By recording the positions of fossils in geological strata, paleontologists deduce that: Fossils of organisms found in the deeper rock strata lived much longer ago than those species fossilized in the younger strata.
What is the driving force / mechanism by which evolution occurs
Natural selection
EVOLUTION ‘theory’ proposes:
When natural selection happens enough times to change the gene pool within a population, then
evolution has occurred.
Criteria for evolution by NS
- THERE IS NATURAL GENETIC VARIATION IN POPULATIONS.
- More offspring ARE PRODUCED THAN REQUIRED.
- THERE MUST BE COMPETITION FOR RESOURCES
- ENVIRONMENTAL CHANGE .
- THERE MUST BE Survival of the fittest (most suited).
Outcome of NS
- Organisms of pop better adapted to environment over time
- Causes gene pool of pop to change over time
- If gene pool changes a lot individuals from the new population can no longer breed and produce fertile offspring with the individuals from the ancestral population ( SPECIATION )
Artificial selection
HUMANS selecting and breeding organisms with desirable characteristics
- to produce offspring with those characteristics that will be of some use to humans, eg horticulture, “garden” agriculture, transport, companionship and leisure.
- Only those organisms with the desired trait are allowed to reproduce
What are the differences between artificial and natural selection?
The selection force is
- HUMANS decide which characteristic
are DESIRABLE
- NATURE / ENVIRONMENT
determines which characteristics will
SURVIVE
Selection is in response to:
- Satisfying human needs
- Suitability/adaptation to the environment
Occurs
-Within one or more different species
- Within a single species
Artificial selection in crop plants
- Deliberate interbreeding of closely or distantly related individuals of a species
- to produce new crop varieties with desirable characteristics.
- Native Americans selectively interbred
a wild grass, “teosinte”
with a subspecies, Zea mays into MAIZE (large cobs) skillful breeding
What is speciation
The process whereby a new species evolves
What is a species
A group of organisms which have the same characteristics and are able to breed amongst themselves and produce viable offspring
What is a population
Group of organisms of the same species living in the same area and are able to interbreed
What are the 2 methods whereby speciation occurs
- Geographic isolation
- Reproductive isolation
Explain Geographic isolation
- When a new species is formed as a result of geographic isolation (barriers) from the ancestral species. (Most common form of speciation in animals but not in plants)
- If a population of a single species pg 10
- becomes separated by a geographical barrier (ocean, river, mountains),
- then the population splits into two populations.
- There is now no gene flow between the two
populations. - Since each population may be exposed to different
environmental conditions, - natural selection occurs independently in each of the
two populations - such that the individuals of the 2 populations differ
from each other both genotypically & phenotypically. - Even if the 2 populations were to mix again,
- they will not be able to interbreed.
- They have become different species.
Explain Reproductive isolation
- A mechanism that prevents two or more species from exchanging genes, (i.e. interbreeding) and producing viable, fertile hybrids even though they are not geographically separated
- When one species gives rise to two new species, the two species cannot reproduce with each other even if they do mix. They remain separate due to mechanisms that restrict gene flow between them
- Mechanisms of
reproductive isolation- Breeding at different times of the year
- Speciesspecific courtship behaviour
- Adaptation to different pollinators (plants)
- Infertile offspring in cross species hybrids
- Prevention of fertilization
