overproduction of offspring the species with the characteristics needed to
survive and live to the next generation and reproduce. This trend will lead
to the extinction of the individuals with the unfavorable characteristics,
who could not survive, and the growth of the population with the
Topic: 4 – Ecology and Evolution
Sub-topic: 4.3 – Evolution
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favorable characteristics and these organisms are the ones that reproduce
exponentially.
4.3.4 1 State that the members of a species show variation.
The members of a species show variation.
4.3.5 3 Explain how sexual reproduction promotes variation in a species by
meiosis and fertilization.
The plants and animals depend on sexual reproduction for variation
because sexual reproduction mixes alleles and puts them together at
random to determine an individuals genotype. During meiosis,
homologous chromosomes, those that are inherited from each parent, trade
by crossing some of their genes with the others. Homologous
chromosomes then separate randomly into different gametes. And each
gamete from each individual carries extensively in their genetic makeup
and each zygote made by a mating pair has a unique assortment of alleles.
Every population has a large number of organisms that are capable of
mating so this is what makes the opportunity for variance to take place on
a larger scale.
4.3.6 3 Explain how natural selection leads to the increased reproduction of
individuals with favorable heritable variations. Use the Darwin-Wallace
Theory.
Topic: 4 – Ecology and Evolution
Sub-topic: 4.3 – Evolution
Page: 3
Charles Darwin theory of natural selection is broken up into three
inferences based on five observations. First Darwin found that if all
individuals reproduce successfully than the population size would grow
exponentially. Second, populations tend to stay stable in size if not
disturbed by seasonal fluctuations. Third, environmental resources are
limited. From these three major observations he made his first inference
that there is more offspring than can survive because of the environmental
carrying capacity therefore there is a struggle for existence. An inference
he made was that having the ability to survive and reproduce leads to
gradual changes in a population, with the favorable traits accumulating
over time. He then made two more observations; there is a variation
among individuals of a species and many of these variations are inherited.
From all these observations he then concluded with two more inferences.
Survival depends a lot on the inherited characteristics that best fit the
environment so they survive and reproduce.
4.3.7 3 Discuss the theory that species evolve by natural selection.
Natural selection is the unequal ability of individuals to survive and
reproduce. Natural selection occurs through interactions of environment
and favorable variations of individuals. But the evolution of individuals
because populations are the smallest unit capable of evolving. Species can
Topic: 4 – Ecology and Evolution
Sub-topic: 4.3 – Evolution
Page: 4
inherit variations from their parents, but acquired characteristics are not
affected. Natural selection and variations in species depends on the region
and environment in which the species lives. Therefore, variations caused
by natural selection result in evolution of species.
4.3.8 3 Explain two examples of evolution in response to environmental change;
one must be antibiotic resistance in bacteria.
A good example of evolution in response to environmental change is the
peppered moth evolving in the 1900’s during the Industrial Revolution in
England. There are two variations of the peppered moth, a gray molted
form and a dark-gray colored form. Before the Industrial Revolution the
gray colored moth were the most common because the color enabled them
to camouflage themselves against the lichen covered trees, unlike the darker
colored moths. However, during the Revolution, the trees became cover in
soot, allowing the darker colored moths survive, reproduce, and eventually
outnumber the lighter gray colored moths. This is an example of how the
peppered moth populations have evolved. Another example of evolution
caused my environmental changes is antibiotic resistance to Penicillin
caused by overuse and misuse. Penicillin was prescribed to many people to
help with various things that Penicillin might not have been necessary for,
this mistake was made by doctors over-prescribing it to patients for minor
things that could have been cured with other over-the-counter drugs.
Topic: 4 – Ecology and Evolution
Sub-topic: 4.3 – Evolution
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Another mistake made by patients using Penicillin is the fact that they
would not finish the bottle even if instructed to do so. If the whole amount
is not taken, the drug will not work correctly or completely, and will make
the body immune to it.