Do NowWhat different ways do these animals use to move about?

What traits does each animal have that help it move about as it does?

Unit 5 Evolution

Ch. 15 Darwin’s Theory of Evolution

The Puzzle of Life’s DiversityEvolution - modern organisms have

descended from ancient organisms (change over time)

Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world

Voyage of the BeagleCharles Darwin contributed most to our

understanding of evolutionHe made observations & collected

evidence that led him to propose a hypothesis about the way life changes over time

Voyage of the BeagleThat hypothesis, now supported by a

large amount of evidence, has become the theory of evolution

Darwin’s ObservationsDarwin collected the preserved remains

of ancient organisms - FossilsSome of these fossils resembled

organisms that were still aliveOthers looked unlike any creature ever

seen

Darwin’s ObservationsThe Galapagos Islands influenced Darwin

the mostHe observed that the characteristics of

animals & plants varied among the different Islands

Darwin Presents His CaseDarwin published the results of his work

in a book, On the Origin of SpeciesIn his book, he proposed a mechanism for

evolution called natural selectionHe stated that evolution has been taking

place for millions of years, & continues in all living things

Friday “Dangerous Mind” Movie on Darwin (complete worksheet) Remember!!! Reward Friday

Home Work (Monday)Computer time required at home or

library. One page required

Choose 1 to write aboutCompare Darwin’s and Wallace’s

theories. Compare and contrast both Darwin’s and

Wallace’s careers and background.

Genetics Test

An Ancient, Changing EarthHutton & Lyell helped scientists

recognize that Earth is millions of years old

They also noted that the processes that changed Earth in the past are the same processes that are changing Earth now

Lamarck’s Evolution Hypothesis

The year that Darwin was born, Lamarck published his hypothesis

He proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime

Over time, this process led to change in a species

Lamarck’s Explanation

Population GrowthEnglish economist, Malthus, published a

book, noting that babies were being born faster than people were dying

He stated that if the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone

Inherited Variation & Artificial Selection

Artificial selection - nature provided the variation, & humans selected those variations that they found useful

It has produced diverse plants & animals by selectively breeding for different traits

Evolution by Natural SelectionStruggle for existence - the members of

each species compete regularly to obtain food, living space, & other necessities of lifePredators that are faster & better at catching

prey are more likely to survive

Evolution by Natural SelectionFitness - the ability of the organism to

survive & reproduce in its specific environment.Fitness is the result of adaptations

Evolution by Natural SelectionAdaptation - any inherited characteristic

that increases an organisms’ chance of survivalSuccessful adaptations allow

organisms to become better suited to their environ. & thus better able to survive

Evolution by Natural SelectionIndividuals that are better suited to their

environ., with adaptations that enable fitness, survive & reproduce most successfully - Survival of the Fittest

Evolution by Natural SelectionSince it is similar to artificial selection,

Darwin referred to survival of the fittest as - Natural Selection

In both AS & NS, only certain individuals of a population produce new individuals

Evolution by Natural SelectionHowever, in NS, the traits being selected,

& therefore, increasing over time, contribute to an organism’s fitness

NS takes place without human control or direction

Evolution by Natural SelectionNS results in changes in the inherited

characteristics of a population, that increase a species’ fitness in its environ.

Over time, NS produces organisms that have different structures, & occupy different habitats

Evolution by Natural SelectionAs a result, species today look different

from their ancestorsEach living species has descended, with

changes, from other species over time - Descent with Modification

Evolution by Natural SelectionDescent with modification also implies

that all living organisms are related to each other

Common descent - all species (living & extinct) were derived from common ancestors

Evidence of EvolutionDarwin argued that living things have

been evolving on Earth for millions of years

Evidence of this could be found: in the fossil record, the geographical distribution of living species, homologous structures of living organisms, & similarities in early development

Evidence of EvolutionThe Fossil Record:

Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time

Evidence of EvolutionGeographic Distribution of Living

Species:Darwin realized that similar animals in

different locations were the product of different lines of evolutionary descent

Evidence of EvolutionHomologous Body Structures:

Homologous structures - structures that have different mature forms but develop from the same embryonic tissues

Not all homologous structures serve important functions

Organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs

Homologous Structures

Evidence of EvolutionHomologous Body Structures:

Vestigial organs - may resemble miniature legs, tails, or other structures, a trace of a homologous structure

Evidence of EvolutionSimilarities in Early Development:

The early stages or embryos, of many animals with backbones are very similar

Summary of Darwin’s TheoryIndividual organisms differ, & some of

this variation is heritableOrganisms produce more offspring than

can survive, & many that do survive do not reproduce

Summary of Darwin’s TheoryBecause more organisms are produced

than can survive, they compete for limited resources

Individuals best suited to their environ., survive & reproduce most successfully

Summary of Darwin’s TheoryThese organisms pass their heritable traits

to their offspringThis process of NS causes species to

change over time

Summary of Darwin’s TheorySpecies alive today are descended with

modification from ancestral species that lived in the distant past

This process, where diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life