EVOLUTION AND NATURAL SELECTION. Evolution is defined as the change in species over time. Darwin theorized that evolution occurs through a process known as natural selection . This process is broken down into four parts:. Overproduction Genetic Variation Struggle to Survive
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Evolution is defined as the change in species over time. Darwin theorized that evolution occurs through a process known as natural selection. This process is broken down into four parts:
Overproduction is a process in which each species produces more offspring than will survive to maturity.
The individuals in a population are slightly different from each other. Each individual has a unique combination of traits, such as color, size, speed, and the ability to find food. Some traits increase the chances
of survival and
These beneficial traits
are called adaptations.
genetic and can be
Because there is only so much food, water, space, and other resources available in the environment, not all individuals will
live to adulthood.
Those best adapted will
have a better chance of survival. Nature, or the environment selects
which organisms live
and which die. This
struggle is often referred
to as “Survival of the Fittest”.
The individuals that are well adapted to their environment, that is, those that have better traits for living in their environment,
are more likely to survive and reproduce. Their
traits are thereby passed
on to their offspring. Theindividuals that are not well adapted to their environment are more likely to die early or produce few offspring.
When an effective insecticide is used on a population of insects, most insects are killed, but few may survive. These survivors have genes that make them resistant to the
The survivors then reproduce, passing the insecticide-resistant genes to their offspring.
In time, the replacement population of insects is made mostly of individuals that have the insecticide-resistant genes.
Ultimately, when the same kind of insecticide is used on the insects, only a few are killed because
the overall population hasbecome resistant to that insecticide.
Select Video 4 and travel to Ecuador to see how the process of natural selection operates in populations of rainforest hummingbirds.
There are five pieces of evidence scientist use to support the theory of evolution. They are:
Scientists have observed that many different organisms have structures that are quite similar. For instance, when comparing a human hand, cat leg, dolphin flipper, and a bat wing, we find nearly identical bone patterns.
Why would structures specialized for such different functions such as grasping, walking, swimming and flying be so similar? The evolutionist conclusion is that these different animals must have evolved from a common ancestor.
Vestigial structures are structures that no longer serve a function in the living organism. For instance, humans have a tail bone that serves no apparent function. In addition, the modern whale has a series of bones near the base of the skeleton that resemble hip bones. Hip bones serve the function of allowing land animals to walk. Why would a whale have hip bones? The evolutionist conclusion is that the whale must haveevolved from a land walking creature.
Fossil evidence also supports the theory that the modern day whale evolved from a land walking animal.
50 Million Years Ago
55 Million Years Ago
46 Million Years Ago
40 Million Years Ago
View Video 3 to see how different lines of
evidence contribute to our picture of
evolution. Learn about the fossil evidence for
whales' land-dwelling ancestors.
A developing baby is called an embryo. Embryos of very different organisms such as a chicken, rabbit, and human have embryos that look nearly identical. During the early stages of development, all have a tiny tail and gill slits in their throats. The conclusion is that all of these organisms have a commonEMBRYONIC STUCTURES
ancestor. It is thought that the embryo is like a window through evolutionary time. The ancestors of these species once had tails and gills.
The DNA that codes for all life on this planet is composed of the same four nitrogen bases, adenine, guanine, cytosine, and thymine. In addition, this coded message creates the same twenty amino acids that builds all life forms on the planet. This similarity, according to the theory of evolution, suggests that all life on the planet has evolved from a common ancestor.DNA EVIDENCE
Select Video 5 and examine the fossil and molecular evidence that supports the evolution of humans from earlier primate ancestors.