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Introduction to Evolution Biology – Ch 16 Where did all organisms come from? Why such variety? 1.

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Presentation on theme: "Introduction to Evolution Biology – Ch 16 Where did all organisms come from? Why such variety? 1."— Presentation transcript:

1 Introduction to Evolution Biology – Ch 16 Where did all organisms come from? Why such variety? 1

2 Darwins Voyage Five year voyage around the world collecting 1000s of specimens & recording 1000s pages of notes 2

3 Darwins Observations Patterns of Diversity Different parts of the world exhibited slightly different, but similar organisms Similar phenotypes Africa and South America Galapagos Islands – see next slide! Fossil evidence Ancient similar organisms? Culminate in Theory of Evolution 3

4 Galapagos Tortoises Different islands = different tortoise shells 4

5 Galapagos Finches 5

6 6

7 Darwins Influenced by others The world is ancient and continually changing MUCH older than previously thought Continually changes – not fixed Populations grows faster than the environment can support them Leads to competition for existing resources: food, shelter, locations Characteristics are inherited, not acquired during a lifetime Characteristics that allow organisms to survive better can reproduce more offspring The survival trait gets passed on to offspring 7

8 Darwins Concepts 8 Inherited Variation Observed that members of any species vary from one another in nature Observed that breeders are able to get desired traits in animals by breeding together those animals that exhibit the wanted traits The traits randomly occurred in nature Named Artificial selection since helped by humans

9 9 Struggle for existence Organisms produce more offspring than can naturally survive Produces a struggle for existence – resources, space, mates

10 10 Survival of the Fittest Struggle for existence led to only the most fit surviving and having offspring The ability of an individual to survive and reproduce in an environment is fitness Anatomical Structural Behavioral (The BEST definition)

11 11 With time, natural selection results in changes in the inherited traits of a population. These changes can increase a species fitness in an environment. Descent with Modification Over a vey long period of time, natural selection produces organisms that have different structures, establish different ways of surviving, or occupy different habitats so that organisms today look different from their ancestors

12 Evolution Evidence 12 Fossils – showed that organisms have been around and changing for millions of years Geographical distribution of living species – similarity of species around the world in similar environments Homologous structures of living organisms – similar anatomical structures in different species led to the idea that they may have had a common ancestor Similar embryonic development – embryos of many animals with backbones look similar

13 13 Fossil Evidence

14 14 Geographic Distribution of Living Organisms

15 15 Homologous Body Structures

16 16 Similar embryonic development

17 Summary of Darwins Theory 17 Individual organisms differ - some of these variations are heritable Organisms produce more offspring than can survive. Some survivors do not reproduce Due to overcrowding in an environment, there is competition for limited resources Each organism has unique characteristics that can help it survive or not. Individuals that have characteristics that allow them to survive and reproduce successfully, produce more offspring and pass along these traits to their offspring. (Survival of the fittest) Species alive today have descended, and changed, from ancestors in the distant past (Descent with modification)

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