evolution€¦ · is evolution just a theory? •in everyday language, a theory can be a careless...
TRANSCRIPT
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Evolution
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Evolution• Evolution is a
generation to generation change in the proportion of different inheritedgenes in a populationthat account for all the changes that have transformed life over an immense time (i.e. a change in populations over time)
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Evolution• Microevolution is evolution
on the smallest scale -generation to generation change in the frequencies of alleles within a population (short-term)
– Alleles are different forms of a gene (ex. T or t)
– A population is a group of individuals of one species living in a particular area
• Microevolution leads to changes in the “gene pool,” all the alleles in a population’s genes
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Evolution
• MACROEVOLUTION is a major biological change evident in the fossil record, includes speciation(development of an entirely new species).
• Macroevolution works on a long time scale that create and destroy species.
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Is Evolution Just a Theory? Isn’t evolution just a theory?
How does the scientific meaning of a term like “theory” differ in the way that it is used in everyday life?
What are some other commonly accepted scientific theories?
What is an inference?
Can the facts of science change over time? If so, how?
If you say:Evolution’s
JUST a theory.
I hear:
I have no idea what “theory”
means.
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Is Evolution Just a Theory?• In everyday language, a theory can be a careless idea – a
hunch or a guess.
• In science: Theories pull together observations, inferences, laws, and hypotheses into coherent
explanations. These theories are tested and supported with scientific evidence.
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Is Evolution Just a Theory? Other commonly accepted theories include:
The heliocentric model of the universe (the Earth revolves around the Sun)
Cell Theory (all organisms are made of cells)
Atomic Theory (all matter is composed of atoms)
Germ Theory (pathogens cause disease)
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Is Evolution Just a Theory?
• INFERENCES are conclusions based on observations/ available evidence.
• The fossil record and genes support Darwin’s inference that organisms descended from a common ancestor.
• With new discoveries, the details of scientific theories are refined. Theories are constantly challenged and amended.
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• Biologists have no doubt that evolution occurred.
• They even know what drives it: o The growth of any population beyond
the ability of the environment to support them
o The appearance of novel genetic traitso The greater growth of some of those
variant organisms leading to changed populations
• But biologists are still debating the details of how it occurs. The theory of evolution, like any other scientific theory, is being continually revised and refined.
Is Evolution Just a Theory?
What does it mean that evolution is a theory?
(Answer in your own words)
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Lamarck’s Theory of Evolution
• Proposed that evolution occurs through the inheritance of acquiredcharacteristics (1809)
• Organisms develop new traits by usingor not using body parts (called the law of use and disuse)– If a body part were used, it got stronger
– If a body part were not used, it deteriorated
• Said acquired traits were passed on to offspring
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Lamarck’s Theory of EvolutionA giraffe’s neck increasing in length over time from stretching to
reach leaves on tall tree branches is an example of Lamarck’s theory of inheritance of acquired characteristics.
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Lamarck’s Theory of Evolution• Inheritance Of Acquired Traits
– According to Lamarck, traits Acquired During Ones Lifetime Would Be Passed To Offspring
Can clipped ears of dogs be passed to offspring? Why or why not?
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Voyage of the Beagle
Charles Darwin• Born Feb. 12, 1809
• Developed the idea of Natural Selection as the mechanism for evolution after observing organisms on a 5 year voyage on the HMS Beagle, 1831
• Published On The Origin of Species in 1859
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Darwin Left England in 1831.The purpose of the mission was to chart poorly known stretches of the South
American coastline for the British navy.
Darwin returned 5 years later in 1836
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The Galapagos Islands
• Volcanic islands off the coast of South America
• Island species varied from mainland species & from island-to-island species.
• Each island had long or short neck tortoises. Neck length varied depending on the climate and foodavailability.
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The Galapagos Islands• Darwin observed finches on the islands that resembled a mainland
finch, but had slight differences (beak shape).• More types of finches appeared on the islands where the available
food was different (seeds, insects, etc.)• They had different beaks adapted to their food type.
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The Galapagos Islands
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Darwin’s Observations
• Individuals of a population varyextensively in their characteristics with no two individuals being exactly alike.
• Differences among members of the same species is called VARIATION.
• Much of this variation between individuals is inheritable.
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Darwin’s Conclusion• Individuals with inherited
characteristics well-suited to their environment are likely to leave more offspring than less adapted individuals
• Survival of the fittest
• Called Natural Selection
The green beetles have been selected against and the brown beetles have flourished.
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•In terms of evolution, an organism is NOT fit in the sense that it is buff and can lift weights
•Darwinian fitness is determined by an organism’s ability to survive and reproduceto pass on traits.
Darwnian Fitness
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• Natural selection is four condition process that leads to the gradual changes we observe in organisms
1. There must be a variation in a population• Organisms can vary in height,
color, and many other traits• In sexual reproducers, this
variation often comes from the random assortment of genes in meiosis
• In asexual reproducers, this variation comes from mutations, errors in DNA replication
Natural Selection
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2. More individuals are born in a generation than will survive to reproduce
3. Survival is NOT random. Those organisms that survive have a variation in a trait that gives them an advantage.
Natural Selection
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4. The advantageous trait must be heritable, so that it can be pass on to future generations.• If an organism cannot
pass its traits, the organism’s evolutionary fitness is ZERO
Natural Selection
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• Mutations in the genetic code can provide a population with novel traits.
• These mutations could have beneficial, negative, or neutraleffects on the organism’s survival.
Mutations Provide Random Variation
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The large ears of the jackrabbit are an adaptation to the animal’s
hot environment. Rich with blood vessels, the ears radiate
heat, which helps cool the jackrabbits body.
• An adaptation is an inheritedcharacteristic that improves an organism’s ability to survive and reproduce in a particular environment.
• Adaptations result from genetic variation.
• Adaptations improve fitness –the contribution that an individual makes to the gene pool of the next generation compared to the contribution of other individuals.
Adaptations
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Other examples of adaptations…
• Elephant Ear Plant: Large leaves on this forest floor plant absorb more light for photosynthesis
• Gerenuk – have hips that rotate in such a way to allow them to stand on their hind legs
• Pitcher plant: an insect-eating plant that has small containers at the end of each leaf. They contain liquids to attract insects.
• Octopus – can shoot ink to distract predators
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Adaptations Vs. Variations• Adaptations:
– Determined by DNA
– Are a change in characteristics
– Are inheritable
– Improve fitness
– Increase an organism’s chance of survival
– Increase an organism’s chance of producing offspring
• Variations:– Determined by DNA
– Are a change in characteristics
– Are inheritable
– Does NOT improve fitness
– Does NOT increase an organism’s chance of survival
– Does NOT increase an organism’s chance of producing offspring
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What’s the Connection Between Adaptations and Evolution?
• Organisms that are better adapted to their environment are more likely to survive and pass these traits on to their offspring. This is NATURAL SELECTION.
• Over periods of time, the frequency of certain traits within a population will change. This is an example of evolution.
Fill Out Venn Diagram
Inheritable
Improves fitness
Does NOT improve fitness
Determined by DNA
Change in Characteristics
Increases an organisms chance of survival
Does NOT increase an organisms chance of survival
Increases an organisms chance of having offspring
Does NOT increase an organisms chance of having offspring