Natural Selection
Published November 2018
www.BioInteractive.org
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Activity
Student Handout
Developing an Explanation for Tuskless Elephants
INTRODUCTION
Most African elephants have tusks, but typically about 6% of females in a population will never grow tusks. Adult
males are very rarely found without tusks. However, in Gorongosa National Park in Mozambique, 50% of
females over 20 years old are tuskless, and 33% of females between 10 and 20 years old are tuskless.
Why are there so many tuskless females in the Gorongosa elephant population? To answer this question, you
Gorongosa National Park, watch these two BioInteractive Scientists at Work videos: the first minute of
The Great Elephant Census and all of Selection for Tuskless Elephants
. As you watch the videos, complete
the questions from the “Task 1” handout.
II. Scientific Explanation of Evolution by Natural Selection. Using a “Scientific Explanation of Evolution by
Natural Selection” chart, construct an explanation for the high incidence of tusklessness in the
Gorongosa elephant population.
III. Argumentation. Develop an argument to answer the question “Will the trend toward increased
tusklessness in a population with heavy poaching lead to increased African elephant population sizes in
the future?” The goal of this task is for you to make a prediction about the future of these populations
using evidence and reasoning from the previous tasks.
Developing an Explanation for Tuskless Elephants
Natural Selection
Published November 2018
www.BioInteractive.org
Page 2 of 5
Activity
Student Handout
1. Look up the definition of the term poaching and summarize your understanding of what it means in the
space below.
2. Watch the first minute of The Great Elephant Census
a. What are the main threats to African elephant populations?
b. The estimated rate of elephant loss is ______ elephants per day.
3. Research the location of the country of Mozambique. Draw an arrow pointing to Mozambique on the map.
4. Watch the entire Selection for Tuskless Elephants
video and answer the following questions.
a. Joyce Poole is an expert in ___________________________________________.
b. What happened in Mozambique between 1977 and 1992? How did this event affect the size of
Gorongosa National Park’s elephant population?
c. What is unusual about the elephant populations found in Gorongosa now?
d. What are tusks? How does an elephant use its tusks?
e. What would probably happen to a male elephant that doesn’t have tusks?
Therefore, tusklessness in male elephants is a ___________ (rare/common) trait.
Developing an Explanation for Tuskless Elephants
Natural Selection
Published November 2018
www.BioInteractive.org
Page 3 of 5
Activity
Student Handout
f. What percentage of females are typically tuskless in an elephant population less affected by poaching?
g. Tusklessness is an ______________ (inherited/acquired) trait. Tuskless females tend to have
______________ (tusked/tuskless) offspring.
h. Why were elephants with tusks targeted during the civil war in Mozambique?
i. What percentage of female elephants were tuskless in Gorongosa according to Pooles surveys? Write
Civil War Survivors
(20+ years old)
Offspring of Civil War Survivors
(10-20 years old)
% tuskless females
j. How many adult males without tusks have been found in Gorongosa National Park? ________________
k. Is the link between heavy poaching and a high incidence of tuskless females unique to Gorongosa? Cite
Task II. Scientific Explanation of Evolution by Natural Selection
Write an explanation based on natural selection for the high incidence of tusklessness among female elephants
in Gorongosa. Like all good scientific explanations, your explanation should include a claim, supporting evidence,
and scientific reasoning to link the evidence to the claim. Use the Scientific Explanation of Evolution by Natural
Selection chart below and on the next page to organize the information you will use in your explanation.
Condition
Description
Evidence
Variation
Individuals in a population or group
differ in some trait of interest.
Inheritance
The variation in the trait of interest is
at least partially inherited (passed
from parents to offspring).
The variation stems from random
mutations and the recombination that
accompanies sexual reproduction. The
genetic variation may have arisen
many generations in the past.
Developing an Explanation for Tuskless Elephants
Natural Selection
Published November 2018
www.BioInteractive.org
Page 4 of 5
Activity
Student Handout
Differential
survival and
reproduction
More offspring are born than can
survive, resulting in competition
among individuals within a population.
Some individuals with a particular trait
are more likely to survive and/or have
relatively more offspring compared to
individuals that do not have that trait.
Selection depends on the specific
context of a species. Traits that are
beneficial in one environment may
cause problems in another
environment.
The frequency of the trait that helps
individuals survive or leave more
offspring will increase in the
population over time, as will the
frequency of the alleles that affect the
trait. This process can take many
generations and extend over very long
periods of time.
Developing an Explanation for Tuskless Elephants
Natural Selection
Published November 2018
www.BioInteractive.org
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Activity
Student Handout