Presentation is loading. Please wait.

Presentation is loading. Please wait.

Evidence for Evolution by Natural Selection

Similar presentations

Presentation on theme: "Evidence for Evolution by Natural Selection"— Presentation transcript:

1 Evidence for Evolution by Natural Selection

2 A BRIEF HISTORY... Charles Darwin
The person who was most influential to our understanding of evolution. In 1831, at age 22, he joined the crew of the HMS Beagle as a naturalist for a 5 year voyage around the world.

3 Darwin’s Findings After Darwin returned to England in 1836 he filled notebooks with his ideas about species diversity and the process that he would later call evolution. He did not rush to publish his ideas because they disagreed with the fundamental scientific beliefs of his day. He asked his wife to publish his ideas when he died.

4 Wallace’s Essay In 1858, another naturalist, Alfred Russell Wallace wrote an essay describing his work in Malaysia that summarized the same ideas Darwin had been thinking about for 25 years.

5 Origin of Species Suddenly Darwin had incentive to publish the results of his work. In 1859, his book On the Origin of Species presented evidence and proposed a mechanism for evolution that he called natural selection.


7 Evolution is NOT goal-oriented
An evolutionary trend does not mean that evolution is goal-oriented. Surviving species do not represent perfection. There is random chance involved as well Traits happen— Well suited to an environment, OR NOT! Evolution is the survival of the fittest, but sometimes it is survival of the just good enough.

8 Evidence supporting evolution
Fossil record shows change over time Anatomical record comparing body structures homology & vestigial structures embryology & development Molecular record comparing protein & DNA sequences Artificial selection Human-caused evolution

9 1. Fossil record Layers of rock contain fossils
new layers cover older ones creates a record over time fossils show a series of organisms have lived on Earth (over a long period of time)

10 Life on Earth has changed
Fossils tell a story… the Earth is old Life is old Life on Earth has changed

11 Evolution of birds Today’s birds descended from ancestral species
Fossil of Archaeopteryx lived about 150 mya links reptiles & birds The avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability. 11

12 Transition from sea to land
2006 fossil discovery of early tetrapod 4 limbs Missing link from sea to land animals

13 We found the fossil — no joke!
Land Mammal ? Complete series of transitional fossils ? Where are the intermediate fossils? ? ? There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan. Ocean Mammal 13

14 2. Anatomical record Animals with different structures on the surface
But when you look under the skin… It tells an evolutionary story of common ancestors

15 How could these very different animals have the same bones?
Compare the bones The same bones under the skin limbs that perform different functions are built from the same bones How could these very different animals have the same bones?

16 Homologous structures
Structures that come from the same origin homo- = same -logous = information Forelimbs of human, cats, whales, & bats same structure on the inside same development in embryo different functionson the outside evidence of common ancestor

17 But don’t be fooled by these…
Analogous structures look similar on the outside same function different structure & development on the inside different origin no evolutionary relationship How is a bird like a bug? Solving a similar problem with a similar solution

18 Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate
both adapted to life in the sea not closely related Watch the tail!

19 Vestigial organs Structures on modern animals that have no function
remains of structures that were functional in ancestors evidence of change over time eyes on blind cave fish human tail bone

20 Because they used to walk on land!
Vestigial organs Hind leg bones on whale fossils pelvis on snake Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

21 They just came up with the same answer!
Convergent evolution Flight evolved 3 separate times — evolving similar solutions to similar “problems” 3 groups with wings Does this mean they have a recent common ancestor? They just came up with the same answer! NO!

22 Convergent evolution led to mimicry
Why do these pairs look so similar? Monarch male poisonous Viceroy male edible Which is the fly vs. the bee? Which is the moth vs. the bee? fly bee moth bumblebee

23 Too close to call for hungry birds!!

24 Yuck!!!

25 Comparative embryology
Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development

26 3. Molecular record Comparing DNA & protein structure
everyone uses the same genetic code! DNA 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 compare common genes compare common proteins number of amino acids different from human hemoglobin

27 Building “family” trees
Closely related species are branches on the tree — coming from a common ancestor

28 “descendants” of wild mustard
4. Artificial selection How do we know natural selection can change a population? we can recreate a similar process “evolution by human selection” “descendants” of wild mustard

29 Humans create the change over time “descendants” of the wolf
Selective Breeding Humans create the change over time “descendants” of the wolf

30 I liked breeding pigeons!
Artificial Selection …and the examples keep coming! I liked breeding pigeons!

31 Unexpected consequences of artificial selection
Pesticide resistance Antibiotic resistance

32 Insecticide resistance
Spray the field, but… insecticide didn’t kill all individuals variation resistant survivors reproduce resistance is inherited insecticide becomes less & less effective The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases. 32

Download ppt "Evidence for Evolution by Natural Selection"

Similar presentations

Ads by Google