CHANGE OVER TIME. Ms. Feierabend

Transcription

1 CHANGE OVER TIME Ms. Feierabend

2 OBJECTIVES Demonstrate the theory of natural selection through historical & modern-day examples. Recognize that variation exists in every population & describe how a variation can help or hinder an organism s survival. Explain how the fossil record documents the appearance, diversification and extinction of many, but not all, life forms. Use internal and external anatomical structures to compare and infer relationships between living organisms as well as those in the fossil record. Discuss why extinction is a common event and can occur when the environment changes & how population's ability to adapt is not enough to allow its survival.

3 DARWIN S OBSERVATIONS Charles Darwin: studied plants and animals on the Galapagos Islands and developed the theory of natural selection. He was amazed by variety of life on the Galapagos Islands. 13 species never seen before, where did they come from?

4 FINCH CLADOGRAM

5 Adaptations to different diets in Darwin s finches

6 NATURAL SELECTION Definition A process by which organisms with traits best suited to their environment are more likely to survive and reproduce. The principles/ideas of natural selection: Organisms produce more offspring than can survive Variations among species occur Variations are passed on to offspring Beneficial variations survive and reproduce better Over time, offspring with beneficial variations will dominate Compare to Lamarck here

7 VARIATION AND ADAPTATION Definition of Variation An inherited trait that makes an individual different from other members of its species. What are some examples of variations? What causes variations? Variations are what allows a SPECIES to adapt over time and can lead to speciation. SPECIATION: the rise of a new species

8 ADAPTATIONS Definition of Adaptation Any variation that makes an organism better suited to its environment. NOT a choice! These are things organisms are born with, don t develop or learn

9 Some spectacular adaptations.

10 EXAMPLES OF CHANGE OVER TIME: Antibiotic resistance in Mycobacterium tuberculosis, MRSA, E.Coli, etc Changes in beak size of Galapagos finches Insects and their resistance to pesticides Peppered Moth in England

11 HOW FAST DOES CHANGE HAPPEN? Gradualism is a model describing change over time as a slow process by which one species changes into a new species through a continuing series of mutations and variations. On the other hand Punctuated Equilibrium is a model describing the fast change that occurs when mutations of a few genes results in a species suddenly changing into a new species.

12

13 Fossils provide evidence of change over time. Fossil: A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust. After remains are buried by sediments: (1) Compression/impression/casts/molds:impressions or casts made before decomposition (like footprints). (2) Permineralized fossils: precipitation of minerals in cells before decomposition. Or Occasionally: (1) Unaltered remains: Frozen, amber embedded, peat bogs.

14 permineralized fossils amber cast Impression fossil

15 Why is the fossil record incomplete? It takes the right conditions at the right time in the right place. - some organisms are not likely to yield fossils - sedimentation does not occur in all habitats - fossils must survive geological events and weather the elements for millions of years before discovery

16 DATING TECHNIQUES One way to find the approximate age of fossils found within a rock layer is relative dating. Relative dating is based on the idea that in undisturbed areas, younger rock layers are deposited on top of older rock layers.

17 Geologic Column Earth s history as told by rock strata

18 DATING TECHNIQUES CONT. Scientists can obtain a more accurate estimate of the age of fossils by using radioactive elements. A radioactive element gives off a steady amount of radiation as it slowly changes to a non-radioactive element. Radiometric Dating is a technique that compares the amount of radioactive and non-radioactive elements in a fossil. (carbon & nitrogen)

19 VESTIGIAL STRUCTURES A structure that doesn t seem to have a function and may once have functioned in the body of an ancestor. Examples: Human appendix (in plant-eaters, a larger appendix-like pouch contains bacteria that allow them to digest woody plants ) human tailbone pelvic girdle (hips) in some whales. cave fish will often lose their eyes over long periods of time

20 Transitional Fossils - an example of a transitional fossil (showing hindlimbs in a fossil whale)

21 FAMILY HOMINIDAE: GREAT APES (CHIMPS, GORILLAS & ORANGUTANS & HUMANS

22 HOMINIDS A Hominid is a humanlike primate that appeared (fossil evidence) about 6 to 4 million years ago, ate both plants &meat, and walked upright on two legs. Humans are the only living hominids.

23 CLADOGRAM OF HOMINIDAE

24 EXTINCTION The moment of extinction is the death of the last individual of that species. Extinction is a common event Nearly 1 billion species have lived and become extinct during the history of life on earth.