ch. 6.2 theory of evolution & natural selection
TRANSCRIPT
• http://learn.genetics.utah.edu/content/selection/recipe/
Lesson 2 Reading Guide - KC
1. Who was Charles Darwin?
2. How does evolution through natural selection work?
3. How do variations become adaptations?
Focus Questions
Lesson 2-1
• Charles Darwin: English naturalist who developed the theory of evolution in the mid-1800s.
• A naturalist is a person who studies plants and animals by observing them.
• Alfred Wallace was another English scientist who is considered the co-creator of the theory of evolution because of his contributions.
1. Who was Charles Darwin?
Lesson 2-1
Darwin found that each island in the Galápagos had a different environment, and tortoises looked different depending on which island environment they inhabited.
Lesson 2-2
• Darwin concluded:
– different tortoises all came from a common ancestor
– Variation (slight differences) occurred later on through natural selection.
• A variation is a slight difference in an inherited trait within a species (as a result of sexual reproduction)
• Variations occur because of genetic mutations (changes to phenotype) can be passed on to future generations by sexual reproduction.
2. How does evolution through natural selection work?
Darwin also studied varieties of mockingbirds and finches. He noticed variation in the types of beaks.
Lesson 2-2
• Natural selection: when an organism has a variation that allows it to live longer, compete better, & reproduce more than those without the variation.
• Natural selection explains how populations change as their environments change.
2. How does evolution through natural selection work?
Lesson 2-2
NATURAL SELECTION:
1. Reproduction:
many offspring
produced
2. Variation:
some offspring
have variations
(ex: longer neck)
3. Competition:
offspring with
longer necks can
eat more food, so
they live longer &
reproduce more
4. Selection:
longer neck
variation is
passed on to
offspring –
eventually all
have longer
necks
Lesson 2-3
• Through natural selection, a helpful variation in one individual can spread to all members of a population.
• Mutations cause variation (differences).
• When many similar variations become more common & give a species an advantage, they are called adaptations.
• An adaptation is an inherited trait that increases an organism’s chance of surviving & reproducing in its environment.
3. How do variations become adaptations?
Lesson 2-3
Types of adaptations:
• Structural adaptations involve color, shape, and other physical characteristics.
• Behavioral adaptations involve the way an organism behaves or acts.
• Functional adaptations involve internal body systems that affect biochemistry.
3. How do variations become adaptations?
Structural Adaptation - Fur coat
Behavioral Adaptation - Grooming
Structural Adaptation - Teeth
Behavioral Adaptation - Vocalization
Functional Adaptation—
regulating body temperature (countercurrent heat exchange system)
Lesson 2-3
• Camouflage and mimicry are adaptations that help species avoid being eaten.
• Camouflage – enables a species to blend in with its environment.
• Mimicry – when one species resembles another species.
3. How do variations become adaptations?
Lesson 2-4
• Selective breeding – the breeding of organisms for desired characteristics.
• Darwin realized that changes caused by selective breeding were much like changes caused by natural selection.
Artificial Selection
Which is an inherited trait that increases an organism’s chance of surviving and reproducing in its environment?
A. Camouflage
B. Adaptation
C. Natural selection
D. Variation
Camoufla
ge
Adaptatio
n
Natura
l sele
ctio
n
Variatio
n
0 000
45
At the park, Ben observes that the dogs are all different sizes and colors. What characteristic is Ben observing?
A. Camouflage
B. Adaptation
C. Natural selection
D. Variation
Camoufla
ge
Adaptatio
n
Natura
l sele
ctio
n
Variatio
n
0 000
45
What term refers to the breeding of organisms for desired characteristics?
A. Adaptation
B. Variation
C. Natural selection
D. Selective breeding
Adaptatio
n
Variatio
n
Natura
l sele
ctio
n
Select
ive b
reedin
g
0 000
45
Which refers to the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than those that do not have the variations?
A. Adaptation
B. Mimicry
C. Natural selection
D. Selective breeding
Adaptatio
n
Mim
icry
Natura
l sele
ctio
n
Select
ive b
reedin
g
0 000
45
Lesson 2 - VS
• Charles Darwin developed his theory of evolution partly by observing organisms in their natural environment.
• Natural selection occurs when organisms with certain variations live longer, compete better, and reproduce more often than organisms that do not have the variations.
Lesson 2 - VS
• Adaptations occur when a beneficial variation is eventually inherited by all members of a population.
Environmental change causes variations in populations?
a. b.
00
a. Yes
b. No
45
Variation can lead to adaptation?
a. b.
00
a. Yes
b. No
45