Download Descent with modification, Fitness as a result of adaptation, and

Descent with modification,
Fitness as a result of
adaptation, and Struggle
for existence.
Descent with Modification
The evolutionary term descent with modification is
most often associated with human evolution, but it is
actually a more general term than that would suggest.
Simply put, descent with modification means that
traits are passed down from generation to generation
and sometimes undergo changes or modifications over
time
These changes may be caused by natural selection, or
even a mutation of DNA.
Descent with Modification
The term became popular when Charles Darwin used
it in his book “The Descent of Man”
On a microevolution level, descent with modification
would indicate a change in DNA that leads to a new or
different adaptation that could be favourable for a
species in that given environment
On a macroevolution level, this term would describe
how a species has changed over time and may have
even become a new species or gave rise to an additional
species through speciation.
Descent with Modification
Descent with modification can be used to describe
changes in a species over generations. For instance,
modern day elephants have the traits they have because
of descent with modification from their ancestors.
Primitive relatives of elephants were as small as a
domestic dog at one point.
Other points throughout an elephant's evolutionary
history had species with long, shaggy hair and
extremely long and curly tusks. Through descent with
modification, the elephant is now a large animal with
smaller tusks and much less hair.
Descent with Modification VS
Natural Selection
Natural selection was Darwin's explanation for how
species changed over time. For example, in a cold
environment where thick fur helps an animal survive,
individuals with a gene for thicker fur may live longer,
which gives them a chance to produce more offspring.
Offspring who inherit the thick-fur gene live longer,
too, producing more descendants, until the thickfurred individuals dominate the population.
Just as a dog breeder selects for particular traits, the
environment also favors traits that enable individuals
to survive and breed.
Descent with Modification VS
Natural Selection
Natural selection and descent with modification may sound
like the same process, but they are not. Genetic
modification(which is how descent with modification
occurs) can happen for multiple reasons besides natural
selection. Some modifications occur because of genetic drift
or horizontal gene transfer.
These modifications of the organisms occurs independent
of selective pressures.
Selective pressures: reason for an adaptation to be necessary
to survive
Example: certain types of beaks were necessary in the Finches
because of the selective pressure of food source.
Descent with Modification VS
Natural Selection
One difference between natural selection and descent
with modification is that natural selection doesn't
appear to create variation or give rise to new genetic
traits. Natural selection works with the genetic mix
already in the population. The environment favors
certain heritable traits over others and may even
influence the expression of some genes, but it can't
favor a heritable trait that doesn't exist.
Genetic modification includes mutation and
horizontal gene transmission, which add new genetic
strains to the population. Without them, the genetic
range of a species would be much more limited.
Fitness as a result of
Adaptation
An adaptation is a feature that is common in a
population because it provides some improved
function.
Fitness: describes how good a particular organism is at
leaving offspring in the next generation relative to how
good other organisms are at it.
If brown beetles consistently leave more offspring than
green beetles because of their color, you'd say that the
brown beetles had a higher fitness.
Fitness as a result of
Adaptation
Fitness is a relative thing. An organism's fitness
depends on the environment in which the organism
lives. The fittest organism during an ice age, for
example, is probably not the fittest genotype once the
ice age is over.
The fittest individual is not necessarily the strongest,
fastest, or biggest. An organisms fitness includes its
ability to survive, find a mate, produce offspring — and
ultimately leave its genes in the next generation.
So the phrase “Fitness as a result of adaptation” just
means an organism is able to survive, find a mate, and
reproduce due to an adaptation which was
advantageous for it.
Struggle for existence
Continuous struggle for existence in nature, from
which only the “fittest” will survive.
There are far too many organisms that are produced in
comparison to the amount of resources available on
the planet.
Therefore, to sustain an environment, there is a natural
struggle for existence.
Struggle for existence
For Darwin, the inevitability of a struggle for survival
was the key to evolution by ‘natural selection’. Any
individual plants and animals that happened to vary in
an advantageous way would be more likely to triumph
over their competitors.
This struggle took many forms
Predators
Food/Territory
Competition for mate
Extreme weather
Struggle for existence
Predators
Struggle for existence when predators are always on the
look out for prey. Organisms with a better chance of
camouflaging, or escaping the predator have a better
chance of surviving. Therefore, the won the struggle for
existence
Food
Struggle for existence when the type of food sources
available are better suited to one organism compared to
another. The organism with the disadvantage loses the
struggle and dies.
Struggle for existence
Competition for mate
Competition for mate can also be a struggle for
existence. That is because some animals have to either
fight a male competitor for a female, or have to be more
impressive than the male rival. Therefore, whoever gets
the female can then reproduce, and has won the
struggle for existence
Extreme weather
Weather can also be a factor in this portion. If an
organism resides in a hot and dry climate, they are more
likely to survive if they aren’t furry, whereas if they
reside in a cold environment, they would survive.