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Chapter 6 Adaptations Over Time.

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1 Chapter 6 Adaptations Over Time

2 Ch Evolution A. Evolution – changes in inherited characteristics of a species over time 1. A species is a group of organisms that share similar characteristics and can produce fertile offspring

3 B. Early Models of Evolution 1
B. Early Models of Evolution 1. Acquired characteristics – proposed by Jean Baptiste de Lamarck 2. Suggested that traits developed during an organisms life time could be inherited by future offspring 3. This theory was not supported by evidence

4 C. Darwin’s Model of Evolution
1. Charles Darwin observed that species of finches on the Galapagos Islands looked similar to mainland finch species

5 2. Darwin hypothesized that plants and animals on the Galapagos Islands off the coast of South America originally came from Central and South America

6 3. He reasoned that members of a population best able to survive and reproduce will pass their traits to the next generation 4. Over time these differences result in new species

7 5. Darwin’s hypothesis became known as the theory of evolution by natural selection “ Organisms with traits best suited to their environment will more likely survive and reproduce.”

8 D. Variation – an inherited trait that makes an individual different from other members of its species 1. An adaptation is a variation that makes an individual better suited to its environment


10 2. Many environmental factors can cause changes in the sources of genes 3. Geographic isolation can make 2 populations so different that they can become different species

11 E. Speed of Evolution 1. Gradualism – describes evolution as a slow, ongoing process 2. Punctuated Equilibrium – model says gene mutation can result in a new species in a relatively short time

12 Ch 6.2 – Clues About Evolution
A. Direct Evidence of Evolution 1. Fossils – found in sedimentary rock show that living things evolved 2. Bacteria – development of antibiotic resistance in bacteria

13 B. Fossils age can be determined by 2 methods: 1
B. Fossils age can be determined by 2 methods: 1. Relative Dating – looks at fossil location in particular layer of rock; older rock layers are under newer rock layers

14 2. Radiometric & Carbon Dating – compares the amount of radioactive element or carbon with the amount that does not contain these

15 C. Fossil records have gaps 1
C. Fossil records have gaps 1. Incomplete rock record b/c most organisms do not become fossils 2. Enough fossils have been discovered for scientists to conclude that complex organisms appeared after simpler ones 3. Most organisms that have ever existed are now extinct

16 D. Indirect Evidence of Evolution 1
D. Indirect Evidence of Evolution 1. Embryology – the study of embryos and their development shows similarities among all vertebrate species

17 2. Homologous body parts – can indicate that 2 or more species share a common ancestor

18 3. Vestigial Structures – structures that do not seem to have a function but might have once functioned in an ancestor

19 4. DNA – can provide evidence about how closely related organisms are
Human – 23 pairs chromosomes Ape – 24 pairs


21 Ch 6.3 – Evolution of Primates

22 A. Primates – group of mammals with opposable thumbs, binocular vision and flexible shoulders
Lemurs, Tarsiers, Monkeys, Apes & Humans

23 Lemurs, Tarsiers, Monkeys, Apes & Humans

24 1. Hominids - appeared about 4-6 million years ago and had larger brains than apes

25 2. Fossils such as Australopithicus point to Africa as the origin of hominids

26 3. Homo habilis and Homo erectus – are thought to be early human ancestors

27 B. Homo sapiens – “Wise Human” began evolving about 400,000 years ago 1. Neanderthals – had short, heavy bodies with thick bones, small chins and heavy brow ridges a) Disappeared about 30,000 years ago b) Not thought to be a direct ancestor to modern day humans


29 2. Cro-Magnon humans – fossils date from around 10,000-40,000 years ago a) Are thought to be a direct ancestor to early Homo sapiens


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