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Natural Selection/Evolution, image, Start Here ⬇️, End Here and go back up…
Natural Selection/Evolution
Evolution is a theory
Scientific theory - explanation of observed facts that is supported by such a wide body of evidence
There is no significant contradictory evidence
Scientifically accepted as factual framework
The Father of Evolution: Charles Darwin
Although Charles Darwin is the father of evolution, he was NOT the first to propose evolution
Darwin had many influences that helped shape his theory
Jean-Baptiste Lamark
Proposed one of the first theories of evolution in the early 1800s
Inheritance of Acquired Characteristics
acquired vs. inherited characteristics
Believed that change occurs over time
Weisman Experiment
Cut off the tails of mice and the offspring all had long tails
Other ideas that helped shaped Darwin's Theory
Thomas Malthus
English economist argued that when a human population gets too large, competition will break out
This will keep populations in check by killing off the weakest members
Charles Lyell
Geological process have gradually shaped the Earth’s surface and the earth continues to change
Artificial Selection
Process of selection made by Humans
Nature provides the variation
Humans choose what to breed
Faster than Natural selection
The Theory of Evolution by Natural Selection
Every Population has variation
Each member of a species is genetically unique
These differences in DNA lead to different phenotypes being expressed
Some variations will be more favorable than others in the environment
The environment acts as the selecting agent determining which organisms are better adapted (those that have better traits).
Those organisms with better traits will survive and reproduce more successfully than others
Those traits are passed onto the next generation
What causes variation?
Mutations in the DNA
Missense mutations
Mutations cannot be willed into existence, they are random!
Variations during sexual reproduction—meiosis
Crossing over
random fertilization
independent assortment
overproduction
A population produces more offspring than can survive
They do this for a better chance of their offspring to survive. Nemo was the only one who survived.
Competition
organisms must compete for resources
food, shelter, mates are limited
individuals in a population compete for limited resources. those with favorable variations will be more likely to survive and reproduce
those without, will die.
Adaptations
A phenotype that improves an organism's chance of survival in a particular environment
Can be three different types:
Structural (morphological)
Physiological (internal)
behavioral
Survival of the Fittest
Organisms with better adaptations in the given environment will survive and reproduce in greater numbers
The ultimate goal is to survive long enough to reproduce and pass on your genes
Fitness = reproductive success
Even if an organism is strong and fast– their fitness is zero if they do not reproduce.
The offspring with the highest % or most offspring surviving to adulthood is most fit because the offspring can then reproduce
Important to remember
Natural selection does not cause mutations or create new phenotypes
It only selects phenotypes already present in population that maximize fitness.
Types of Natural Selection
Stabilizing
towards the median
Directional
towards one extreme
Diversifying
towards both extremes
image
link to www.google.com
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