The ancestor giraffes had short necks. - PowerPoint Presentation

Slide1

The ancestor giraffes had short necks.

The ancestor giraffes lengthened their necks by stretching to reach leaves.The longer neck was passed on to offspring.Whose theory of evolution is this?Lamarck’sSlide2

Lamarck’s Hypothesis – Not SupportedAccording to Lamarck’s hypothesis

, organisms are striving for perfection.Organisms can change their features to be perfectly suited for their environment.Does this look like a “perfect” organism to you?

Winter FlounderSlide3

Darwin’s Hypothesis – Well SupportedAccording to

Darwin’s hypothesis, organisms evolved by a process called natural selection.What is natural selection?Slide4

Natural SelectionWhat is

natural selection & how does it drive evolution?Slide5

What do you think is about to happen?Slide6

Natural SelectionThe process by which organisms who are better adapted to their environment will survive & reproduce

Some giraffes have long necks, but some giraffes have short necks.Which giraffes are probably better adapted for their environment?The taller giraffes are more likely to survive & pass down their genes to offspring.Slide7

Natural Selection – “Survival of the Fittest”

Fitness: ability to survive & reproduceHigh fitness means best adapted, not necessarily the strongest.

Some beavers have large, strong teeth, but some beavers have small, weak teeth.

Which beavers probably have the higher fitness?

The beavers with strong teeth are more likely to survive & pass down their genes to offspring.Slide8

How does natural selection cause evolution?Slide9

Variation Within a SpeciesDifferent individuals within a species have differences in their morphology

& physiology.Morphology: the form or shape of an organismPhysiology: the mechanical, physical, & biochemical functions of living organisms

Morphology

PhysiologySlide10

Morphology

– some of us are tall, while some of us are short.Physiology – some of us have a fast metabolism, while some of us have a slow metabolism.Slide11

Morphology – some cats have long legs, but some cats have short legs.

Physiology – some cats can digest cow milk, but some cats can’t.Slide12

These differences change the ability of an organism to survive & reproduce (fitness).Some peppered moths are black & some are white.

This variation allows some individuals to survive better than others.The moths that survive will reproduce & pass down beneficial traits.Which moths have the higher fitness?The black moths have a higher fitness than the white moths. They will survive & pass on the black gene to offspring.Slide13

AdaptationAny inherited characteristic that increases an organism’s chance of survival & ability to

reproduceIncreases fitnessCamels store fat in their humps to help them survive long periods without food/water. This is an adaptation that gets passed down from parent to offspring.Slide14

A mouse has learned how to avoid mousetraps, increasing its chances of survival.

Is this an adaptation?NO!Learned behaviors are NOT adaptations, because they’re not carried in genes, so they don’t get passed on to offspring.An adaptation is a trait that is coded for in genes, allowing it to be passed from parent to offspring.Slide15

Fitness & AdaptationsThose individuals that have a higher fitness will pass on their morphological & physiological differences to their offspring.

Which mouse has the higher fitness?The tan mouse blends in better, & therefore will survive better.The tan mouse is more likely to reproduce & pass down the tan gene to offspring.Slide16

Selective PressuresOver time, populations change based on the selective pressures of the environment.

Selective Pressure: any factor that makes it hard for some organisms to continue surviving, & rewards any advantage that some organisms may have been born withThe selective pressure in an environment is what determines which organisms have a high fitness & which ones have a low fitness.Selective pressures drive populations to evolve.Slide17

Selective PressuresClimate ChangesFood Supply ChangesPredators

Sexual SelectionWhat type of selective pressure do you think affects this moth population?Predators make it difficult for white moths to survive, giving them a lower fitness.The black moths have the advantage, so they will contribute genes to the next generation.Slide18

Antibiotic Resistance

What’s the selective pressure driving this population to evolve?Slide19

Large ground finches use their large beaks to open seeds.Let’s say that the area has had an ideal amount of rainfall, so the plants are able to grow much larger.

Since the plants are larger, the seeds are also much bigger.Now, only the finches with the biggest beaks can eat.The finches with smaller beaks don’t eat, so they don’t survive & reproduce.The finches with large beaks survive & pass on their “good genes” to the next generation.

What do you think the beak sizes will look like in the next generation?

The next generation of finches will probably have larger beaks – that is evolution by NS!Slide20

The Main Ideas of Natural SelectionOrganisms produce more offspring than can possibly survive.Those that do not survive do not reproduce, & therefore do not pass down their genes.

Each organism has different advantages & disadvantages in the struggle for existence.Individuals best suited for their environment survive & reproduce most successfully.Slide21

The Main Ideas of Natural Selection“Survival of the Fittest”Adaptations are inherited

, NOT learned!Adaptations may be an advantage in 1 environment, but a disadvantage in another.Natural selection only acts on heritable traits.

A mouse that has

learned

how to

avoid mousetraps

does not pass that down to its offspring in its genes

.

This is not an adaptation.Slide22

Peppered moths in the industrial revolutionhttp://www.utdanacenter.org/texteams/downloads/scienceresources/pradeep_fla.swf