Charles Darwin was a British biologist who developed the theory of evolution by natural selection. He proposed that over generations, natural selection causes populations to adapt to their environments as individuals with heritable traits that aid survival and reproduction will leave more offspring. According to Darwin, all species descended from a small number of original life forms that evolved over time through natural selection. Genes are passed down from parents and can mutate, leading to variation within populations on which natural selection acts.

1. ACTIVITY 1
Charles Darwin was a British biologist who postulated the
natural selection hypothesis of biological evolution. Darwin
defined evolution as "descent with modification," the concept
that species change over time, give rise to new species, and share
a common ancestor. Darwin proposed natural selection as the
mechanism for evolution. Because natural resources are finite,
organisms with heritable features that benefit survival and
reproduction will tend to leave more offspring than their
contemporaries, increasing the frequency of the traits over
generations. Natural selection causes populations to adapt to
their environments over time, or become increasingly well-suited
to them. Natural selection is influenced by the environment and
necessitates the presence of heritable variation within a group.
All species, according to Charles Darwin, descended from a
small number of lifeforms that had been modified over time. This
"descent with modification," as he called it, is the foundation of
his Theory of Evolution, which states that certain species evolve
over time by the emergence of new types of organisms from
existent types of organisms. The passing on of traits from parent
organisms to their offspring is referred to as descent with
modification. Heredity is the term for the process of passing on
qualities, and the gene is the basic unit of heredity.
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2. ACTIVITY 1
Genes are the blueprints for constructing an organism, and as such, they
contain information on every aspect of its development, behavior,
appearance, physiology, and reproduction. The transmission of genes
isn't always precise. Parts of the blueprints may be replicated erroneously,
or genes from one parent organism may be mixed with genes from
another parent organism in sexually reproducing organisms. As a result,
children are not identical replicas of either of their parents. It's crucial to
remember that genes and individuals don't evolve; only populations as a
whole do. This is how it works: Genes mutate, and these mutations have
repercussions for individuals within a species. Genetics determines
whether such individuals prosper or perish. As a result, populations
change over time.
Within all populations of creatures, there is variation. This is due in
part to the fact that random mutations can develop in an organism's DNA,
and children can inherit these mutations. Individuals' genes interact with
their environments throughout their lives, resulting in phenotypic
variations. The molecular biology of the cell, other cells, other individuals,
communities, and species, as well as the abiotic environment, make up a
genome's environment. The population evolves because individuals with
particular variants of the trait tend to live and reproduce more than those
with less successful versions. Sexual selection (now commonly included
in natural selection) and fecundity selection are two further processes
that influence reproductive success.
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The phrase "struggle for existence" was coined by Charles
Darwin in a broader sense, and it was chosen as the title of the
third chapter of On the Origin of Species, published in 1859.
Darwin was able to construct his perspective of adaptation, which
was immensely influential in the formation of the theory of natural
selection, by using Malthus's idea of the fight for existence.
Humans use artificial selection, often known as "selective
breeding," to choose desirable qualities in agricultural products or
animals, rather than allowing species to evolve and change
naturally without human intervention, as natural selection does.
Dog breeding is an excellent example of how humans choose
qualities that are desirable or fashionable. Breeders purposefully
pair parents to produce kids with specified characteristics, such as
color, size, ear shape, snout length, and etc.
Organisms can adapt to their surroundings in a variety of
ways. They can adapt biologically, which means they can change
body functions. The bodies of people living at high elevations,
such as in Tibet, are an example of biological adaptability. Tibetans
thrive at altitudes where oxygen concentrations are up to 40%
lower than at sea level.
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4. ACTIVITY 1
Most individuals would become sick if they breathed air that thin, but
Tibetans' bodies have evolved alterations in their body chemistry.
Because their bodies elevate their levels of hemoglobin, a protein that
transports oxygen in the blood, most individuals can survive at high
altitudes for a short time. However, because sustained high amounts
of hemoglobin are harmful, increasing hemoglobin levels is not a good
long-term option for high-altitude survival. Tibetans appear to have
evolved genetic alterations that allow them to utilize oxygen more
efficiently without requiring additional hemoglobin.
Because many students confuse natural selection with descent
and modification, it's worth repeating and clarifying that natural
selection is an aspect of, but not the process of evolution. According
to Darwin, natural selection occurs when a species as a whole adapts
to its environment due to its unique genetic makeup. Let's pretend
there were two types of wolves in the Arctic at one time: those with
short, thin fur and those with long, thick fur. Long, thick-fured wolves
were genetically capable of surviving in the cold. Those with thin,
short fur were exempt. As a result, wolves with traits that allowed
them to thrive in their environment lived longer, reproduced more
frequently, and passed on their genes. It was "naturally selected" for
them to thrive. Those wolves that were not genetically acclimated to
the cold died out gradually. Furthermore, natural selection does not
generate variety or new genetic features; rather, it selects for genes
that are already present in a population.
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In other words, the Arctic environment in which our wolves lived
did not prompt a succession of genetic features that didn't already
live in certain of the wolf individuals. Mutation and horizontal gene
transmission for example, the mechanism by which bacteria develop
immune to specific antibiotics rather than natural selection
contribute new genetic strains to a population. For example, if a
bacterium acquires an antibiotic resistance gene, it has a better
chance of surviving. Natural selection propagates the resistance
across the population, prompting scientists to develop a new
antibiotic.
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