The Gene Scene The Importance of Genetic Diversity within a Population

General Background  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  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  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  Start at the inner band and locate your appropriate trait, continue moving outward  Example  Class-wide results

Part II - Instructions  2 groups; stand along opposite ends of the classroom  I am going to call out characteristics. If anyone on either team possesses that characteristic they “die” (sit down).  Objective: have at least one team member alive at the end

Part II - Discussion  Did any characteristics wipe out more people on your team than other?  Did one team do better than the other? Why?

Part II – Round Two  Same demonstration  This time make any adjustments you wish prior to starting

Part II - Discussion  Did your team last longer this time?  What helped or hurt your team?  What can you say about how genetic diversity might help wild populations of animals of plants survive?

Part III – Introduction & Setup  Break into groups of 2  Read “All About White-Tailed Deer”  Deer Population  20 Total  10 Females (white paper)  10 Males (green paper)  Determine a Dominant Male Deer  Can be any male  Mark with a “D”  Only this male can mate during reproduction events

Part III – Introduction & Setup  Determine the genetic number of each member of your deer population  Some deer may have the same number  Determine the genetic diversity of your group of white- tailed deer  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 Genetic Combinations

Part III – Introduction & Setup  Cut apart all 20 fawn cards

Part III – Rules  If a white-tailed deer dies, place an “X” over it  Only the dominant male can mate with females  If he dies, pick a new one  If all males or females die, you can no longer reproduce  Some events effect half the population. If your population is an odd number, round down.  Example: population of 17; 8 affected  Female fawns can not reproduce

Part III - Rules  During reproduction events, only qualifying females receive a fawn card  Choose fawn traits based only on the traits of that female and the dominant male  Circle the traits on the fawn card Qualifying FemaleDominant MaleFawn Excellent hearingPoor hearingExcellent OR Poor hearing (your choice) Resistant to disease +Resistant to disease =Resistant to disease (must) Poor sense of smellGood sense of smellPoor OR Good smell (your choice) Large home rangeLarge home rangeLarge home range (must)

Part III - Events  Event 1 –  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  Event 2 –  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  Event 3 –  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  Event 4 –  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  Event 5 –  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  Event 6 –  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  Event 7 –  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  Record on the board the number of white-tailed deer (adults and fawns) surviving in your group  Which group(s) were most successful?  Did genetic diversity contribute to this? How?

Part III - Analysis  Did some traits seem to be favored over other?  “Resistant to disease” favored over “not resistant to disease”  When EHD virus struck  “Good sense of smell” favored over “poor sense of smell”  Fawns vulnerability to coyotes  Females find males to mate  “Excellent hearing” favored over “poor hearing”  Poachers  “Large home range” favored over “small home range”  Drought  Habitat fragmentation  3 fawns versus 1 fawn

Part III - Analysis  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.  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  Why is genetic diversity important to the survival of a species?’  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  What is the relationship between the size of a population and its genetic diversity?  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  What can be done to prevent loss of genetic diversity?  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