Presentation is loading. Please wait.

Presentation is loading. Please wait.

Defined: the process of biological change by which descendants come to differ from their ancestors. o 5 factors that lead to evolution: 1.Genetic drift.

Similar presentations


Presentation on theme: "Defined: the process of biological change by which descendants come to differ from their ancestors. o 5 factors that lead to evolution: 1.Genetic drift."— Presentation transcript:

1

2

3 Defined: the process of biological change by which descendants come to differ from their ancestors. o 5 factors that lead to evolution: 1.Genetic drift 2.Gene flow 3.Mutations 4.Sexual selection 5.Natural Selection

4 Species Species: group of organisms that can interbreed and produce fertile offspring – Different species rarely breed – Interspecies (between different species) breeding often results in sterile offspring Ex: Horse x Donkey = Mule Ex: Lion x Tiger = Liger

5

6 Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth. – Cause: environmental changes forced individuals to change – Problem: Traits acquired after fertilization cannot be passed to offspring Early Belief: Giraffes & Long Necks – Long necks are result of stretching to reach leaves – Extra length was passed on to offspring

7 Geologic Change Early belief: – Earth ~6,000 years old – Life remained unchanged “New” Observations – Rock layers (strata) contained differing fossils – Deeper fossils (older) less complex – Environmental changes thought to affect life characteristics

8 Charles Darwin Observed: – Organisms have variations based upon environment – Similarities between extinct fossils & modern life – Marine fossils atop mountains Natural Selection: Process where organisms with favorable traits survive and reproduce Major concept in biology published in The Origin of Species (1859)

9 Finches are another example. – Finches with strong, thick beaks live in areas with a lot of large, hard shell nuts. – Finches with delicate beaks live in areas where small insects and fruits are readily available.

10 Adaptation & Variation Variation: Inherited traits that make an individual different from others – Green, flat wings of the insect above Adaptation: Variation increases the chance of survival – Ability to blend with environment

11

12

13

14 Causes of Genetic Variation Genetic variation increases chances some organisms survive in changing environments Gene Pool: All alleles within a population Two main causes of genetic variation: 1) Mutations: Random genetic changes may affect phenotypes 2) Recombination: During meiosis, genes recombine in varying patterns

15 Variation: 4 Different Gametes Chromatids copied Chromatids copied Crossing- over Crossing- over Crossing- Over finished Crossing- Over finished Genetic variation! Four differing chromatids Genetic variation! Four differing chromatids

16 Features of a species can evolve, or change over time Natural selection is when favorable traits allow survival & reproduction Variations allow an organism to be better suited to its environment


Download ppt "Defined: the process of biological change by which descendants come to differ from their ancestors. o 5 factors that lead to evolution: 1.Genetic drift."

Similar presentations


Ads by Google