What is the evidence for evolution?

Transcription

1 What is the evidence for evolution? 1. Geographic Distribution 2. Fossil Evidence & Transitional Species 3. Comparative Anatomy 1. Homologous Structures 2. Analogous Structures 3. Vestigial Structures 4. Comparative Embryology 5. Genetic (DNA) Comparisons

2 I. Geographic Distribution Related native species are found only where they could have migrated on their own

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4 II. THE FOSSIL RECORD

5 Importance II. THE FOSSIL RECORD Provides the best proof of the history of life showing how extinct species have led to today s species Lucy, 3.2 MY Archaeopteryx, 150 MY

6 Completeness of the Fossil Record?

7 Transitional Species (Common Ancestors) Location where two species evolutionary path connect on the tree of life Intermediates between old and new species Importance of Transitional Species Scientists search for common ancestors in the fossil record to show the evolutionary connection between species & how they change over time.

8 Transitional Species Ex: modern horse descended from dog-sized animal with multiple toes

9 The Mammalian Family Tree A dead end branch represents an extinction. Where is the most recent common ancestor between squirrels and whales? All these species can trace their lineage back to this common ancestor, essentially the first mammal.

10 Cladogram

11 Transitional Species: Land Mammals to Aquatic Mammals

12 WHALES HAVE LEG BONES! Vestigial structures leftover from when the whale s ancestors walked on land

13 Ancient landdwelling ancestors Once again, there is gradual progression in the fossil record, and new fossils are being discovered all the time. The gradual change can even be seen in the evolution of the blowhole. Modern baleen whales

14 III. Comparative Anatomy Homologous Structures Analogous Structures Vestigial Structures

15 Homologous Structures traits inherited by two different organisms from a common ancestor that have the similar structures, but have adapted different functions. Homologous structures support the idea of a shared common ancestor EX: vertebrate forelimb bones

16 Analogous Structures Unrelated species with structures that may look and function similarly but are made up of parts that do not share a common evolutionary path showing no connection to a common ancestor. These similarities usually exist because the unrelated species are adapting to similar environmental conditions. EX: wings for flight and fins for swimming

17 A Human Which limbs are Homologous and which are Analogous in each set? Why? B Octopus Human Lizard Lizard Bird Whale Grasshopper

18 species A species B adaptation #1

19 adaptation species A species B adaptation #2

20 Diagram 1 below illustrates how the eagle and the penguin evolved their wings from earlier birds. Diagram 2 shows how birds and bats evolved their wings separately, and in different ways. species A adaptation species B Homologous traits adaptation species A Analogous traits species B adaptation Diagram 1 Diagram 2

21 Think.. If analogous adaptations are NOT inherited from a common ancestor, then how can they be considered evidence for evolution? What do they show us about the process?

22 Vestigial Structures Structures that are found in an organism but appear to serve NO function (reduced in size) they are remnants or left overs of an organism s evolutionary past Ex: Whales and snakes have pelvic bones; manatees sea cows have finger nails on their fins Humans?

23 Tailbone Wisdom teeth. Remnant of earlier primate ancestors with tails Leftover from our ancestors with larger jaws This is why wisdom teeth are so commonly removed. Modern humans jaws tend to be too small, so the teeth get impacted. Some people never even develop wisdom teeth.

24 The same muscles (arectores pilorum) that enable a cat to do this: also enable us to do this:

25 Hiccups, which occur in many other animals, are a result of a nerve misfiring and telling your epiglottis to close off your trachea. Its purpose can be traced back to the first organisms with lungs (which incidentally still had functioning gills as well). This function can still be seen in modern tadpoles. It s what keeps their lungs from filling up with water while they re still using their gills.

26 Homologous Or Not??

27 Answers 1. No (they do not share a common ancestor with wings) 2. No (they do not share a common ancestor with fins) 3. Yes (both are birds that have adapted different uses for their wings) 4. Yes (both are insects that evolved from insects with wings) 5. Yes (all are types of modified leaves from different plants) 6. No (they do not share a common ancestor without limbs) 7. Yes (both are in the primate family which all have opposable thumbs) 8. Yes (both are mammals with modified front teeth) 9. No (they are not closely related, fish and reptile, scales evolved independently) 10. No (they are different groups of mammals, placental and marsupial, that do not share gliding ancestors)

28 IV. Comparative Embryology Similarities in the developmental pattern of organisms exist because of a common ancestor vestigial gill slits/pouches bony tail covered in a fine hair Two chambered hearts Which is a chicken, pig and human? Human embryo Pig embryo Chicken embryo

29 Can you guess what type of animal this is?

30 Can you guess what type of animal this is? Turtle embryo See the developing shell?

31 Comparative Embryology in Vertebrates All vertebrates (related species) are similar in early stages of development. Differences accumulate as development continues. New development instructions are added to old instructions inherited from common ancestors.

32 Comparative Embryology in Vertebrates

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34 Human embryo 5 weeks after conception 1 cm

35 What animal is this? Notice the leg buds Spotted dolphin

36 Both embryos at about 5 weeks gestation!

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38 V. Comparing Genetics An organism s evolutionary history is held in their DNA sequence (genetic code) If a species changes, their DNA changes Genetic testing compares the similarity of DNA between organisms The more closely related the species are to each other the more similarities they share in their DNA Ex: Chimpanzees & Humans have over 98% the same DNA

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40 What is the evidence for evolution? 1. Geographic Distribution 2. Fossil Evidence & Transitional Species 3. Comparative Anatomy 1. Homologous Structures 2. Analogous Structures 3. Vestigial Structures 4. Comparative Embryology 5. Genetic (DNA) Comparisons