Download Continuous variations

Teacher's Notes
Subject: Biology
Lesson: Evolution: variation and natural selection
Topic:
Environmental and inherited causes of variation
Grades: 7-9
In order for evolution to occur, there has to be variation. Variation within a species increases the chance that some
members of the species will survive changes in the environment. Depending on environmental conditions,
inherited characteristics may be advantageous, detrimental, or neutral to the survival of the individual. Natural
selection occurs when factors in the environment select for or against certain variations.
Lesson Objectives
By the end of this lesson, students:
understand why variation is important to the
survival of a species
identify examples of discrete and
continuous variation
distinguish inherited and environmental
causes of variation
Lesson Notes
Prior Knowledge:
species
population
genes
Major lesson points:
Discrete and continuous variation
Genetic and environmental causes of variation
The role of variation in evolution
The lesson concludes with an assessment
of the students learning of the lesson concepts
and objectives.
Terms and Definitions
Write your response,
and then pull tabs for answers.
Question 1: Why is variation important to the process of
natural selection and evolution?
Variation defines the differences among individuals of a species. It allows some individuals in a species to survive while
others perish.
Question 2: Why is variation important for species survival?
Nature chooses the best suited variation and allows the characteristic to continue in the gene pool.
Question 3: What does it mean to be ‘fit’ in terms of
natural selection?
Fitness: the most ‘fit’ individual has the highest number of surviving offspring.
Types of Variation: Discrete and Continuous
Sort the types of variation.
Discrete variation means an individual either has the trait or they don’t. Discrete variations are caused by genetic changes and
are controlled by a single gene or a small number of genes.
Continuous variations are measured on a continuum, come in a range of forms, and are
controlled by a combination of many genes.
The environment can have a significant influence on continuous variations, but little effect on discrete variations.
Types of Variation: Inherited and Environmental
Touch blue text to reveal information.
Inherited Variation
An individual’s genes determine the inherited
characteristics.
Environmental Variation
Differences in the environment lead to variation.
Without the proper environment (nutrition, sun, water), the genetic instructions can’t overcome the
environmental influence.
Eye color, skin color and
hair color are inherited traits.
Hydrangeas grow pink flowers in alkaline soil and blue in acidic soil.
Two trees with the same genes can grow to different heights, depending
Even identical twins don’t turn out identical.
on environmental factors such sunlight, water and nutrition.
Environmental influences always cause variation.
The environment can influence inherited traits.
Variation is necessary for survival.
Touch image multiple times to reveal information about the evolution of the peppered moth.
What is the role of variation in species development?
Move a set of birds to each island. Touch the clock to start time. Drag each new bird to the island
you believe it evolved on.
Why should we care about variation today?
Touch the numbers to reveal.
1
A mutation causes
an individual in a
strain of bacteria
to be resistant to
antibiotics.
With the normal
bacteria dead,
the resistant
bacteria multiply
and become more
common.
3
Antibiotics kill
most of the
normal bacteria.
2
The resistant strain
takes over.
The antibiotic is no
longer effective.
4
1
Multiple Choice
Height is a _______ and _______ characteristic.
A
non-heritable, continuous
B
heritable, continuous
C
non-heritable, discrete
D
heritable, discrete
Review
Put the tiles in order.
1)
2)
3)
4)
5)
Characteristic
is more common
Mutation
becomes
part of the (mutation).
Individual
born with
afavorable
favorable
characteristic
Offspring
with
characteristic
in
future
generations.
pool
and species
evolves.
Individual
survives and reproduces.
have a highgene
rate of
survival.
Answer
1)
Individual born with a favorable characteristic (mutation).
2)
3)
Individual survives and reproduces.
4)
Offspring with favorable characteristic have a high rate of survival.
5)
Characteristic is more common in future generations.
Mutation becomes part of the gene pool and species evolves.
2
Multiple Choice
Blood type is a _______ and ______ variation.
A
non-heritable, continuous
B
heritable, continuous
C
non-heritable, discrete
D
heritable, discrete
3
Multiple Choice
The most ‘fit’ moths ________.
A
are peppered
B
are black
C
are white
D
blend with the environment
4
Multiple Choice
Which is an example of an environmental variation?
A
eye color
B
earlobe attachment
C
hydrangea flower color
D
hair color
5
Multiple Choice
Select all that apply.
Choose the example(s) of continuous variation.
A
tongue rolling
B
foot length
C
eye color
D
height
6
Multiple Choice
Variations in weight are ______.
A
completely due to genetics
B
completely due to the environment
C
heritable with environmental influences
D
environmental with heritable influences
7
Multiple Choice
Having an attached earlobe is a ______ and ______ characteristic.
A
non-heritable, continuous
B
heritable, continuous
C
non-heritable, discrete
D
heritable, discrete
8
Multiple Choice
Variations can be ______.
A
neutral
B
helpful
C
harmful
D
all of the above
Why did the finch’s beak shape change over time?
Use pen to write answer.
Different food was available on each island. Birds
with beaks the right shape to get the food survived.
Over time, the differences in beak shape became
more distinct until they became different species.
Why should we be concerned about variations in bacteria?
Use pen to write answer.
The ‘fittest’ bacteria survive, requiring us to
continue to develop new antibiotics and
leaving us defenseless against them.