High School Biology : Understanding Biological Fitness

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Biological Fitness

Biological fitness is defined as __________.

Possible Answers:

the ability of an organism to survive and reproduce

the average life span of an organism

the percentage of energy that is dedicated to mating

the amount of energy an organism can use in the environment

Correct answer:

the ability of an organism to survive and reproduce

Explanation:

The biological fitness of an organism is dependent on its ability to survive and reproduce in a given environment. If different traits or alleles increase the fitness of an organism, those alleles will consequently increase in the gene pool, and that trait will increase in the population. This is how natural selection affects a population.

There is inherent trade-off in biological fitness. A trait that increases ability to survive, but makes an individual sterile, decreases fitness because the organism cannot produce offspring to carry on the trait. Similarly, if a trait increases the ability to reproduce, but makes it harder to the organism to survive, it may die before being able to produce offspring. Both survival and reproduction are essential to defining the fitness of an organism.

Example Question #2 : Understanding Biological Fitness

Which of the following best describes biological fitness?

Possible Answers:

Ability to reproduce

Ability to grow to the largest size

Ability to compete against other organisms

Ability to reason and think logically

Ability to have superior physical strength

Correct answer:

Ability to reproduce

Explanation:

Biological fitness in the evolutionary sense is only related to fitness in terms to reproduction. Because the primary goal of all organisms is to reproduce, or to pass their DNA onto offspring, fitness is defined as the ability to reproduce and create viable offspring.

"Favorable" traits, such as intelligence, size, or strength, may increase the ability of an individual to survive and reproduce, thus increasing biological fitness, but cannot be used to directly define the fitness of the individual.

Example Question #2 : Understanding Biological Fitness

Darwinian fitness is a measure of __________

Possible Answers:

the ability of an organism to kill another organism

the ability of an organism to protect its young

the ability of an organism to run for long periods of time

the ability of an organism to create offspring

the ability of an organism to use tools

Correct answer:

the ability of an organism to create offspring

Explanation:

The term "fitness" in evolutionary biology means the ability of an organism to pass on its genetic material to its offspring. Biological or "Darwinian" fitness is being able to live long enough to reproduce and keep the population or species alive. Most students confuse biological fitness with physical fitness because that is the context most often associated with the word.

Example Question #4 : Understanding Biological Fitness

In the study of evolution, sometimes it is useful to assess the biological fitness of an individual.  What is the best criterion to use to measure the biological fitness of a certain large, strong iguana?

Possible Answers:

The weight of the iguana

The number of predators the iguana has in its environment

The number of the iguana's offspring who also survive to reproduce

The hunting ability of the iguana

The age of the iguana

Correct answer:

The number of the iguana's offspring who also survive to reproduce

Explanation:

Biological or Darwinian fitness is defined based on the specimen's ability to reproduce and generate viable offspring. Essentially, the fitness of the individual is based on its ability to pass genetic information on to the next generation, as opposed to any physical characteristic or trait.

Measuring the number of offspring who contribute to the gene pool is the best way to determine how genetically fit the iguana is. No matter how strong, large, old, or free of predation an animal is, if it cannot reproduce, it is not considered fit.

Example Question #3 : Understanding Biological Fitness

Which of the following is an example of an evolutionary advantage?

Possible Answers:

A bird with a beak that can crack nuts in an environment where nuts are the main food source

A cheetah that can run faster than the rest of his pack

A white rabbit that lives in a snow covered environment

All of these

A black moth that lives near an industrial site that produces a lot of soot

Correct answer:

All of these

Explanation:

All of the examples given provide an evolutionary advantage. A white rabbit in a snow covered environment has camouflage, which protects it from its predators. The same is true with the black moth living in a  in a soot-covered industrial area. A cheeta that can run fastest has the greatest chance of catching prey and feeding himself/herself and his/her offspring. The same is true for a bird that can crack nuts in an area where nuts are the main source of food. 

Example Question #4 : Understanding Biological Fitness

A female cheetah in Africa has four litters of cubs over her lifetime. Her first litter has six cubs that grow to adulthood and is fathered by the most spotted male in the area. Her second litter has four cubs that grow to adulthood and is fathered by the fastest male in the area. Her third litter has two cubs that survive to adulthood and is fathered by the strongest male in the area. Her fourth litter has five cubs that survive to adulthood and is fathered by the smartest male in the area. Which male cheetah has the most biological fitness?

Possible Answers:

The fastest male

Can't tell from the given information

The smartest male

The most spotted male

The strongest male

Correct answer:

The most spotted male

Explanation:

The term biological fitness refers to reproductive success and is different than physical fitness. Since the most spotted male fathered the most cubs that survived to adulthood to reproduce themselves, he would be considered the most biologically fit. It is also important to note the inclusion of the "survived to adulthood" aspect since reproductive success is dependent on an organism's offspring being able to reproduce and contribute to the gene pool as well. For example, if the most spotted male had fathered a litter that initially had nine cubs, but only one of them survived to adulthood to have cubs of its own, he would no longer be considered the most biologically fit.

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