Unit 6 Lesson 4: Differential Reproduction Flashcards
survival of the fittest
a phrase with the same meaning as natural selection
natural selection
the process that results in an organism having favorable adaptations to its environment, which are passed on through reproduction and thus change the genetic makeup of future generations
Darwin was a British naturalist who, as the result of his travels and observations, developed the concept of
survival of the fittest, or evolution by natural selection. Darwin’s ideas were formed before the discovery of genes, so he was not able to explain the process by which some individuals are born with or pass along advantages—but he was able to see and describe the results of genetic advantage.
Besides predators and accessing food, competition can serve as a driver of natural selection as well. In extreme situations, one species can completely outcompete another species for the same resources in the same environment, resulting in the elimination or severe reduction of the other species in an environment. This is known as
competitive exclusion.
Darwin’s ideas were presented in his book On The Origin of Species, which he wrote after years of examining evidence he had collected. In his book, he presented two main processes. The first process was descent with modification. According to this process:
- Traits can be inherited. For example, dark-haired parents are likely to produce dark-haired children; tall parents are likely to produce tall children, and so forth. This is true not only of human beings but also of all plants and animals.
- Each offspring is a little bit different from the others—that is, every individual is unique, creating variation in the population.
The second process was a mechanism he called natural selection. According to this process:
- Most species produce far more offspring than the number that finally survive. Insects and fish, for example, can produce hundreds or even thousands of offspring. Oaks produce thousands of acorns. But only a few offspring survive long enough to reproduce successfully.
- Some individuals will have inherited traits that make them more likely to survive and reproduce successfully. These traits give these individuals a competitive advantage. These individuals are “fitter,” in that they are better adapted to their environment and are more likely to produce offspring.
- Some of the offspring of individuals with competitive advantages will inherit their parents’ helpful traits. They, too, will be more likely to survive and reproduce—and pass along the advantage.
- Over time, most of the members of the species will be offspring of individuals with the same inherited trait that provides a competitive advantage. In other words, the fittest individuals will survive and pass along their strengths to future generations.
Another example of an inherited trait that offers competitive advantage is the owl butterfly. This is a butterfly with an unusual wing pattern that looks extraordinarily like the eye of an owl. How did the owl butterfly happen to develop such a unique wing pattern?
Some researchers believe that the “owl eye” markings on the butterfly deter predators who would ordinarily eat the butterflies. Seeing what looks like an owl causes birds to stay away. The owl eye markings were a competitive advantage passed down from generation to generation until all members of the species shared the same useful wing patterns.
competitive exclusion.
a process by which one species outcompetes another species trying to use the same resources in the same environment, reducing the number of individuals of the other species present in that environment
Example of competitive exclusion
The most classic example of this process is of two species of paramecia, which is a type of single-celled organism commonly found in ponds. If grown together, Paramecium aurelia will outcompete Paramecium caudatum for resources, resulting in the elimination of Paramecium caudatum from the environment.
resource partitioning
when two or more species divide up a resource so they can both coexist in the same environment without having to use the same resources to survive
Example of resource partitioning
For example, both bats and birds may feed on insects, but birds hunt during the day while bats hunt at night.
How did Darwin connect the evolution of a species to the competition caused by organisms that produce far more offspring than are likely to survive?
He believed that the fittest (best adapted) offspring would survive and reproduce, and, by passing along their competitive advantages, they would help the species to evolve.
1.
According to Darwin, advantageous genetic variations among individual members of a species are passed down to offspring.
Is this statement true or false?
false; Darwin did develop the concept of natural selection, but he lived before the discovery of DNA and genes.
How does the discovery of genes help scientists better understand natural selection?
Genetic inheritance explains how some traits are passed from parent to child. Genetic analysis can show when mutations arise and how gene flow helps or hurts a population.
How do advantageous traits in individuals help solve problems for entire species?
Answers should explain the following: Individuals with advantageous traits will survive long enough to reproduce. When they reproduce, they are likely to pass along their advantageous trait. Over time, more and more members of the species will be born with that advantageous trait.
Why might a well-adapted species become extinct?
If a species is well-adapted to a particular environment it might go extinct if the environment changes or if new competition arises for the same resources.
