Theory of Evolution

#2,3, and 4 plus natural selection made easy(1st part)

The theory of evolution describes the ______change in organisms that occurs over many generations. Remember that new evidence suggests that evolution can take place very ______– within two years (Finches of Galapagos Islands).

show - (Isn’t Evolution Just a Theory) (How Do We Know Evolution Happens?) (How Does Evolution Really Work?)

What evidence is there for these slow changes?

The Study of ______has allowed scientists to see these small changes over long lengths of time. The changes of fossil records of a horse.

Many of today’s ideas about evolution are based on the work of Charles ______. Most of these ideas came from observations made during the five years he worked as a naturalist on the research ship H.M.S. Beagle. During this time period Darwin studied 13 different species of Finches (Bird) living on the Galapagos Islands, off the coast of Ecuador. Darwin proposed that all these different finches had evolved (changed) from a single kind of finch found on the mainland of Ecuador. Darwin named this process natural selection.

Natural Selectionis the process whereby ______better adapted to their environment tend to survive and produce more offspring.

An Adaptation is a characteristic or trait that helps an organism ______in its environment. There are two types of adaptations - structural adaptations which deal with the animals actual ______parts such as the cheetah’s large heart, lungs and nostrils which allow them to obtain oxygen to run ______. Camouflage is a common structural adaptation. The second type is behavioral adaptation in which an organism carries out a behavior that it did not need to ______. A common example is birds building a ______– birds do not have to learn to build ______. A human blinking of eyelids when a foreign object is moving close to the eyes is another behavioral adaptation.

Darwin’s main ideas about natural selection are:

  1. Organisms produce many more offspring than can survive. Examples:A female alligator lays 20 to 50 eggs. A baby alligator spends much of its time ______for food in shallow water. It has to stay alert for ______, such as raccoons, snakes, otters, large fish, wading birds, and other animals that will prey on the baby alligators. But many hatchlings still die. Only one out of every ten alligators lives through its first year.Out of 50 eggs laid in the wild only about 3 will ______to adulthood.
  2. There is competition among offspring for food, space, and other resources. Like most large birds of prey, Golden Eagles breed rarely, and usually lay only two ______per nest. Often, one of the eggs hatches with a few days of advantage, and the firstborn chick starts being ______before its sibling is even born. Due to this, the firstborn grows bigger and ______than the younger chick, and usually ______most squabbles for food. If food is very scarce, the younger chick can eventually become weak and is likely to ______because of malnutrition (lack of ______).
  3. There is natural variety (difference) among the offspring of an organism. Individuals within a species vary from one to another. Example: Some of you can run ______while others might have a good ______voice.
  4. Individuals with certain traits are better suited to survive in their environment than those without the traits. Example: The light-colored form of the moth, known as typica, was the predominant form in England prior to the beginning of the industrial revolution. Shown at left bottom, the typica moth's speckled wings are easy to spot against a ______background, but would be difficult to pick out against the ______-colored bark of many trees common in England. Around the middle of the 19th century, however, a new form of the moth began to appear. The first report of a dark-colored peppered moth was made in 1848. By 1895, the frequency in Manchester had reached a reported level of 98% of the moths. This dark-colored form is known as carbonaria, and (as shown at bottom right), it is easiest to see against a ______background. As you can well imagine, carbonaria would be almost invisible against a ______background, just as typica would be difficult to see against a ______background. The increase in carbonaria moths was so dramatic that many naturalists made the immediate suggestion that it had to be the result of the effects of industrial activity on the local landscape. Coal burned during the early decades of the industrial revolution produced very ______gray soot that blanketed the countryside of the industrial areas of England between London and Manchester. The predator birds that fed on the moths could easily see the ______moths but not the ______ones.
  1. Organisms that survive pass their useful ______on to the next generation. Example: The dark moths in the example above passed on the characteristic or trait of being ______in color. That is why 98% of the moths were dark by 1898.