Download Lab 10. Natural Selection

LAB 10: Natural Selection
PRE-LAB QUESTIONS
Name____________________
1. What is evolution?
2. Describe Darwin’s two main points in the Origin of Species.
3. What are the five lines of evidence that support the theory of evolution?
4. What concept involved in evolution will the lab simulate today? Define this concept.
LAB 10: Natural Selection
Natural Selection Simulation
Introduction :
In 1859, biology experienced a big shift in the scientific views on species and how organisms are
interrelated. Charles Darwin published On the Origin of Species by Means of Natural Selection and
shared his views on the natural world based on his observations from his journey aboard the Beagle.
Darwin made two key points in his publication:
1. Current species are the descendents of ancient ancestors.
2. Change to species occurs as a result of “descent with modification” with the cause being natural
selection
Natural selection is a process in which organisms with desirable traits for their environment are
more likely to survive and reproduce than are individuals with other characteristics. Due to natural
selection, a population, a group of individuals of the same species living in the same place at the
same time, changes over time. Natural selection leads to adaptation and an increase in the
frequency of desirable traits for a specific environment. Natural selection directly leads to evolution,
which is a change in the genetic composition of a population over time. As we study evolution, there
are many clues to help us along the way. There are 5 main lines of evidence that support the theory of
evolution.
1.
2.
3.
4.
5.
The fossil record
Biogeography
Comparative Anatomy
Comparative embryology
Molecular Biology
The fossil record shows the appearance of various fossils in an ordered sequence from the oldest to
the most recent. Fossils are the remains of once living organisms that have been preserved through
an impression or a remnant of the organism is left behind. Biogeography is the study of the
geographic distribution of species. Comparative anatomy compares the body structures between
different species and comparative embryology examines the similarities between early stages of
development in different animal species. The advancement of molecular biology has enabled the
hereditary background of organisms to be further investigated by analyzing comparisons at the DNA
and protein level.
Natural selection can be seen in the example of Darwin’s finches, each of these species adapted to the
food resources available on their individual islands and more recently can be seen in antibioticresistant bacteria, pesticide-resistant insects, and drug-resistant strains of HIV.
LAB 10: Natural Selection
Natural Selection Simulation
Overview: Students will model natural selection by using various household utensils to “eat”
available food resources.
Materials for the lab group of 4 students:
1 small paper cup to serve as your stomach
1 of the following per group:
spoon
pair of tweezers
pair of scissors
spring clothespin
toothpick
calculator
stopwatch
Food:
50 beans representing snails
100 segments of rubber bands representing worms
50 mini marshmallows representing fish
100 flakes of cereal representing plants
50 paper clips representing crustaceans
Procedure:
1.
2.
3.
4.
The food items will be mixed together and placed on the lab table within a 4 foot square.
Using only your beak, each of the “birds” must pick up your food and place it in your stomach.
Food can NOT be scooped up or thrown and it must be placed in an upright stomach.
Gather the food item that is easiest first, then switch to a second choice as food resources
become scarce.
5. Feeding time will be limited to 2 minutes.
LAB 10: Natural Selection
Data Collection:
1. Count and record each type of organism you ate in the chart below/
2. Calculate the class average for each food item and each beak.
3. Enter these numbers in your chart in red pencil.
Data Collection- Natural Selection
Name: ____________________
Beak Type
Worms
Scissors
Tweezers
Toothpicks
Spoons
Clothespin
Snails
Food Items
Fish
Crustaceans
Plants
LAB 10: Natural Selection
Name: _________________________
Date: ________________________
POST-LAB QUESTIONS
Natural Selection Simulation
1. Which beak did you have and what was your favorite food? Why?
2. Explain why some beaks were more successful than others.
3. If snails were removed from the estuarine environment, what types of birds would be
affected?
4. What would happen to the population of birds if the most popular food item was
reduced to half? Be specific.
5. Sometimes animals are introduced into an area that they have never lived in before.
Following this introduction, they out-compete and endanger resident species, why do
you think this happens?
6. If only one species is considered the "fittest", why do we still have so many variations
among species? Why do some birds have very long pointy beaks, while other birds have
short flat beaks?
7. How do you think diseases or natural disasters can affect natural selection?
LAB 10: Natural Selection