Transcript The Gene Scene Game

The Gene Scene
The Importance of Genetic Diversity within a Population
General Background
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From a scientific perspective, conserving biodiversity
means more than just protecting the variety of different
species on earth. It also means preserving the natural
variation that exists among the individuals of each
species.
Preserving variety within populations of species
is essential for preserving the ability of that species to
cope with environmental change.
Part I - Background
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Genes are sections of DNA that manifest themselves
as visible traits, such as eye color and hair texture,
and nonvisible traits, such as a susceptibility to a
certain disease
In a healthy population there is a wide variety of genes
that combine in many different ways to form a broad
diversity of individuals.
If the population is suddenly subjected to stress, such as
disease or environmental change, the genetic variety
makes it likely that at least some individuals will be
adapted well enough to survive and continue the species
Part I – Class Genetic Diversity
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Determine your own genetic traits
Check the box that describes the trait you possess on
the “Checking Out Your Genetic Traits”
Use the “Human Genetic Wheel” to determine your
genetic number
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Start at the inner band and locate your appropriate trait,
continue moving outward
Example
Class-wide results
Part II - Instructions
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2 groups; stand along opposite ends of the classroom
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I am going to call out characteristics. If anyone on either
team possesses that characteristic they “die” (sit down).
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Objective: have at least one team member alive at the
end
Part II - Discussion
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Did any characteristics wipe out more people on your
team than other?
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Did one team do better than the other? Why?
Part II – Round Two
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Same demonstration
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This time make any adjustments you wish prior to
starting
Part II - Discussion
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Did your team last longer this time?
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What helped or hurt your team?
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What can you say about how genetic diversity might help
wild populations of animals of plants survive?
Part III – Introduction & Setup
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Break into groups of 2
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Read “All About White-Tailed Deer”
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Deer Population
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20 Total
10 Females (white paper)
10 Males (green paper)
Determine a Dominant Male Deer
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Can be any male
Mark with a “D”
Only this male can mate during reproduction events
Part III – Introduction & Setup
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Determine the genetic number of each member of your
deer population
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Some deer may have the same number
Determine the genetic diversity of your group of whitetailed deer
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How many different genetic numbers are exhibited in your
population
Record your group number and genetic diversity number on
the board
Genetic Numbers of
Individual White-tailed
Deer
5
5
8
11
11
12
12
17 17
17 17
23
24 24
24 24
24 24
30
31
Genetic Combinations
1
2
3
4
5
6
7
8
9
Part III – Introduction & Setup
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Cut apart all 20 fawn cards
Part III – Rules
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If a white-tailed deer dies, place an “X” over it
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Only the dominant male can mate with females
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Some events effect half the population. If your population
is an odd number, round down.
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If he dies, pick a new one
If all males or females die, you can no longer reproduce
Example: population of 17; 8 affected
Female fawns can not reproduce
Part III - Rules
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During reproduction events, only qualifying females
receive a fawn card
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Choose fawn traits based only on the traits of that female and
the dominant male
Circle the traits on the fawn card
Qualifying Female
Dominant Male
Fawn
Excellent hearing
Poor hearing
Excellent OR Poor hearing (your choice)
Resistant to disease
+
Resistant to disease
=
Resistant to disease (must)
Poor sense of smell
Good sense of smell
Poor OR Good smell (your choice)
Large home range
Large home range
Large home range (must)
Part III - Events
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Event 1 –
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The deadly EHD (epizootic hemorrhagic disease), a disease
spread by a virus, is killing many deer. White-tailed deer with
resistance to the disease are much more likely to survive and
reproduce
Lose half of your white-tailed deer population that are
“not resistant to disease”
Part III - Events
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Event 2 –
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Habitat fragmentation has resulted from construction of new
housing developments and an increase in roads. As they move
between the smaller habitats, white-tailed deer have a greater
chance of being hit by cars and trucks on the roads.
Lose one white-tailed deer with a “small home range”
Part III - Events
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Event 3 –
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In the breeding season, males mark their territories with scents
and visit the scented sites often. A female with a good sense of
smell is more likely to know where the male will be when she
is ready to mate, increasing her chances of successful
reproduction.
Add one fawn for each “good sense of smell” female
white-tailed deer.
Assign traits that are present in the parents to the
fawn.
Part III - Events
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Event 4 –
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A severe drought has hit. Because of the extreme dry
conditions, white-tailed deer must travel farther to find food
and water.
Lose one white-tailed deer that has a “small home
range”
Part III - Events
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Event 5 –
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Deer meat, otherwise known as venison, has recently become
popular. Poachers are illegally hunting white-tailed deer after
dark. Deer with poor hearing are easy targets as the poacher
drive up in their vehicles.
Lose half of your white-tailed deer with “poor hearing”
Part III - Events
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Event 6 –
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It has been a mild winter this year, yielding an abundance of
food. Because of good nutrition, all of your female white-tailed
deer give birth in the spring.
Add one fawn for each “small home range” female
white-tailed deer.
Add three fawns for each “large home range” female
white-tailed deer.
Assign traits that are present in the parents of each
fawn.
Part III - Events
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Event 7 –
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Young fawns are particularly vulnerable to predation by
coyotes. A fawn with a poor sense of smell might not be able
to detect a coyote in time to escape.
Lose half of your fawns with a “poor sense of smell”
Part III - Analysis
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Record on the board the number of white-tailed deer
(adults and fawns) surviving in your group
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Which group(s) were most successful?
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Did genetic diversity contribute to this? How?
Part III - Analysis
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Did some traits seem to be favored over other?
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“Resistant to disease” favored over “not resistant to disease”
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“Good sense of smell” favored over “poor sense of smell”
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Fawns vulnerability to coyotes
Females find males to mate
“Excellent hearing” favored over “poor hearing”
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When EHD virus struck
Poachers
“Large home range” favored over “small home range”
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Drought
Habitat fragmentation
3 fawns versus 1 fawn
Part III - Analysis
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It is apparent that certain traits are favored over others
under a specific set of environmental conditions. Is it
possible for this to change? Explain why or why not.
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Yes, it is possible to change. A previously unfavored trait may
become favored if environmental changes occur and vice versa.
Nothing is constant in nature.
A trait that is advantageous under one set of environmental
conditions may be detrimental under another.
For example, in human history, it used to be favorable to have
hairy bodies during the ice age. However, as the climate
warmed this trait went from favorable to unfavorable.
Part III - Analysis
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Why is genetic diversity important to the survival of a
species?’
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A more genetically diverse population is more likely to contain
some individuals that have the traits necessary to survive and
adapt to changes in the environment than populations that
aren’t as genetically diverse.
Part III - Analysis
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What is the relationship between the size of a population
and its genetic diversity?
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As a population becomes smaller, some variation in traits is
lost
Because there are fewer individuals in a smaller population, it is
less likely that there will be individuals with the traits necessary
to survive in times of environmental stress.
This is one reason smaller populations are more vulnerable to
extinction
Many species have lost a great deal of their genetic diversity in
a short time because of habitat loss and overhunting
Part III - Analysis
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What can be done to prevent loss of genetic diversity?
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It is important that wild populations of plants and animals do
not become small or fragmented.
Preservation is becoming more and more challenging as
humans expand and increase their level of consumption as well
as demand for space
Hunting/fishing must be done in a responsible manner