DARWINS THEORY OF EVOLUTION What was Darwins hypothesis

  • Slides: 12
Download presentation
DARWIN’S THEORY OF EVOLUTION What was Darwin’s hypothesis? What is natural selection?

DARWIN’S THEORY OF EVOLUTION What was Darwin’s hypothesis? What is natural selection?

Species: a group of similar organisms that can mate with each other and produce

Species: a group of similar organisms that can mate with each other and produce fertile offspring Adaptation: a trait that increases an organism’s ability to survive and reproduce Evolution: the process of change over time Scientific Theory: a well-tested concept that explains a wide range of observations Natural Selection: the process by which better adapted organisms survive and pass that trait to their offspring Variation: any difference between individuals of the same species

DARWIN AND THE GALAPAGOS ISLANDS A naturalist named Charles Darwin sailed on the HMS

DARWIN AND THE GALAPAGOS ISLANDS A naturalist named Charles Darwin sailed on the HMS Beagle in the 1830 s. Along his voyage around the world, he noted the vast DIVERSITY of living things. At that time, scientists were not able to compile a list of all the living things on Earth, but we now know there at least 1. 6 MILLION species of organisms. Each species is unique in their characteristics and they are able to reproduce and have offspring that can also reproduce. Along his journey, Darwin also found FOSSILS that resembled living things he saw at that present time, but he couldn’t explain what happened to the extinct species.

DARWIN AND THE GALAPAGOS ISLANDS When he arrived at the Galapagos Islands off the

DARWIN AND THE GALAPAGOS ISLANDS When he arrived at the Galapagos Islands off the west coast of South America, he observed many unusual life forms; he noted that some looked similar yet distinctly different to the organisms found on the main land also from island to island. Of particular note, Darwin observed the different species of finches, noting that although their body structures and size remained similar, their BEAKS were different shapes depending upon their food sources on the island. Beak shape is an example of an ADAPTATION, which is a trait that increases an organism’s ability to survive and REPRODUCE.

DARWIN’S HYPOTHESIS After his journey, Darwin continued to study and observe adaptations. Over the

DARWIN’S HYPOTHESIS After his journey, Darwin continued to study and observe adaptations. Over the course of his lifetime, he hypothesized that ALL organisms EVOLVE, or change over time. He hypothesized that the species on the Galapagos Islands changed over many generations to become better ADAPTED to their habitat. Darwin proposed that evolution occurs by means of NATURAL SELECTION. Natural selection is the process in which individuals that are better adapted to their environments are more likely to SURVIVE and reproduce offspring with similar traits. Darwin identified FOUR factors that affect the process of natural selection: � Overproduction � Variation

FACTORS OF NATURAL SELECTION OVERPOPULATION Darwin recognized that most species produce far more OFFSPRING

FACTORS OF NATURAL SELECTION OVERPOPULATION Darwin recognized that most species produce far more OFFSPRING that can possibly survive. Often, so many offspring are produced that there are not enough resources- FOOD, WATER, AND LIVING SPACE -for all of them Q: What happens to the babies if there isn’t enough resources for all the offspring?

FACTORS OF NATURAL SELECTION VARIATION Members of a species DIFFER from one another in

FACTORS OF NATURAL SELECTION VARIATION Members of a species DIFFER from one another in many of their traits. Any difference between individuals in the same SPECIES is called VARIATION. For example: Sea Turtles may differ in color, size, ability to swim quickly, and shell hardness. Q: What are variations we have as humans?

FACTORS OF NATURAL SELECTION COMPETITION Because resources are limited, members of a SPECIES must

FACTORS OF NATURAL SELECTION COMPETITION Because resources are limited, members of a SPECIES must COMPETE with one another to survive. This is not always physical fighting, but can be due to variation. Slower sea turtles, for example, could be eaten by predators. Larger turtles may be able to outmaneuver other members for food. Q: How do giraffes compete for resources? Which variation is favorable?

FACTORS OF NATURAL SELECTION Some VARIATIONS make individuals better suited for their environment. Those

FACTORS OF NATURAL SELECTION Some VARIATIONS make individuals better suited for their environment. Those individuals are more likely to survive and REPRODUCE. Their offspring will likely INHERIT the helpful trait. Then their offspring will likely survive, reproduce, and PASS THE SAME TRAIT. After many generations, more members will have the favorable trait that was naturally selected There is also ARTIFICIAL SELECTION-this is manmade, where humans select special traits they like and breed for that trait. Darwin did this with pigeons. This has occurred more recently in crops, like CORN, and domestic animals, like DOGS.

GENES AND NATURAL SELECTION Darwin could not explain what caused VARIATIONS or how they

GENES AND NATURAL SELECTION Darwin could not explain what caused VARIATIONS or how they were passed on, but we now know that these variations are passed on through DNA and those traits are passed from parents to offspring. These variations may not present themselves until environmental changes occur. Q: Describe the variations among the Peppered Moth species in England before and after the Industrial Revolution.

THE WHITE MICE ARE BEING EATEN, SO THERE ARE ONLY GRAY MICE. THE GRAY

THE WHITE MICE ARE BEING EATEN, SO THERE ARE ONLY GRAY MICE. THE GRAY MICE HAVE THE ADAPTATION OF CAMOUFLAGE (BLENDING WITH THEIR ENVIRONMENT)

The tan mice live longer and have more offspring. Even though it was not

The tan mice live longer and have more offspring. Even though it was not the fastest mouse, it was able to survive because of camouflage. Tan Tyrone because his 95% of his offspring survived until adulthood.