Stimulus and Response Notes

A signal that causes and organism to react in some way

The organism’s reaction to a stimulus.

Variety is when a species has many different physical characteristics.

Over time species’ traits will change/mutate. Especially sexually reproductive organisms because they have 2 parents passing different genes.

If a change is successful it will be passed to the next generation.

Many different adaptations can be successful in the same species.

This contributes to the great variety we see in different species. Ex. Dogs, fish, butterflies.

Nature’s way of picking the best traits to pass on to the next generation.

Due to natural limiting factors (predation, lack of resources) not all individuals get to reproduce to their full potential.

The individuals that reproduce the most/fastest will pass on their traits to the next generation.

Over a period of time, certain traits will be eliminated because of inherent weaknesses.

Some livestock experts, such as Robert Bakewell and Thomas Coke, introduced selective breeding programs to improve the quality of the animals. Bakewell crossed different breeds of sheet to select the best characteristics.

Year 1710 1795 .

Sheep (lbs) 28 80 .

Cattle (lbs) 370 800 .

In 1769, he produced the Longhorn; a breed that was a good meat producer but gave a poor milk yield. His farm, in Dishley, Leicestershire, became a model of scientific management.

The domestic dog is thought to have descended from the gray wolf, and has since evolved to become the most morphologically diverse mammalian species

There are many breeds of dogs today. Dogs are bred for hunting, guarding, herding, and desirable physical characteristics such as skull shape, sixe, and coat variation.

Selective breeding can be used to develop behavioral and physical traits in future generations of animals (creating new breeds).

Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light-colored trees and lichens which they rested upon.

However, because of the widespread pollution during the Industrial Revolution in England, many of the lichens died out, and trees that peppered moths rested on became blackened by soot.

Most of the light-colored moths died off from predation. At the same time, the dark-colored moths flourished because of the their ability to hide on the darkened trees.

Since then, with improved environmental standards, light-colored peppered moths have again become common.

The peppered moth adaptation has become a common example used in explaining or demonstrating natural selection