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Changes over time Life originated from a single-celled organism.

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Presentation on theme: "Changes over time Life originated from a single-celled organism."— Presentation transcript:

1 Changes over time Life originated from a single-celled organism.
Finding a fossils age helps scientists to construct an evolutionary timeline.

2 Three types of Structures
Homologous Vestigial Analogous

3 Homologous Structures
Traits are similar in different species because they share a common ancestor.

4 The Theory of Evolution
Variation, Adaptation, and Evolution

5 Evolution Learning Goals:
Relate variation and adaptation Describe how fossils are used to study ancient-life Analyze Darwin’s theory of evolution Explain how scientists reconstruct history using fossils Identify characteristics defining a species Describe the principles of population genetics Explain the effect of environmental change on populations

6 Variation in a Species A species consists of organisms that mate with each other and that can produce healthy offspring. Differences between individuals in a population is called variation. Ex. Fur color in foxes. Two things can cause variation: mutation and recombination Mutations can be harmful, neutral or beneficial.

7 Causes of Variation *Two things can cause variation: mutation and recombination Mutations can be harmful, neutral or beneficial Beneficial mutations increase the chances of an organism’s survival.

8 Adaptation An adaptation is an inherited trait that increases a population’s chances of survival and reproduction in an environment. Adaptations= advantages that help an organism survive.

9 Biodiversity The many different types of organisms that make up a biologically diverse community. During times of change, populations that are better able to adapt will survive.

10 Natural Selection’s 4 points:
Variation within populations- inherited through traits. Some variations are favored- improves chances of survival Not all young survive- few live to reproduce Individuals that survive and reproduce are those with favorable traits

11 Fossils, a peek into the past
Fossils, or the remains of ancient organisms, help scientists learn about Earth’s history.

12 Changes in the Past All life originated from a common single-celled organism. Finding the age of fossils allows scientists to construct an evolutionary timeline.

13 3 Types of structures Homologous Vestigial Analogous
Similar structures in different species Unused structures that are reduced in size Similar characteristics in different species Share common ancestor No common ancestor. Independent evolution!!!

14 Homologous Structures

15 Causes of Speciation Geographic isolation- members become separated from the original population due to geographic barrier. Examples: mountain range, river ** Reproductive isolation- populations cannot or will not be able to produce offspring.

16 Embryology Animals at the developmental stage of life look similar, but they grow up looking different. Page 385 dragonfly book picture

17 Origin of Species Speciation- is the evolution of one or more species from a single ancestor species.

18 Mechanisms of Evolution
There are 3 types of evolution: Divergent evolution Convergent evolution Coevolution

19 Divergent Evolution Once related populations evolve independently
Often happens because of geographic isolation Ex. Polar Bear and Brown Bear

20 Convergent Evolution Unrelated species have produced (analogous) similar adaptations to help these organisms live in similar environments. Ex. African Serval cat and S.American Maned wolf (pg.242)

21 Coevolution When two or more populations closely interact for a long period of time, they begin to adapt together. Ex. Hummingbirds and flowers. (pg. 243)

22 Adaptive Radiation Evolution of many different, diversely adapted, species from one ancestral species. Ex. Galapagos finch (13 different species)

23 Speciation in Darwin’s Finches
Founders Arrive – birds arrive Separation of Populations- isolated one bird type onto 2 island Changes in Gene Pool – through natural selection, mutation, etc. Reproductive Isolation – new birds don’t cross-breed Ecological Competition – may lead to new bird Continued Evolution – process continues

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