The Perfect Cow?
Lesson Overview

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GRADE LEVEL: Grades 9-12

TIME ALLOTMENT: Two to three 45-minute class periods

OVERVIEW: Cattle evolved through the slow process of natural selection until human domestication, which rapidly accelerated their development as an artificially selected species fit less for survival than to satisfy human needs. This lesson focuses on how and why humans have been so successful in selectively breeding cattle to suit these needs, while also exploring the limitations and consequences of this success.

Natural selection describes the process by which organisms best adapted to their environments are the ones that survive and reproduce. The Introductory Activity helps students understand that some traits, such as the ability to digest grass, made certain species more desirable for domestication by humans. The Learning Activities explore how, by nurturing and protecting animals that might not have survived in the wild, human domestication interrupted the process of natural selection. Reproductive success was no longer primarily determined by an animal’s most naturally adaptive survival traits, but rather by its artificially selected traits desirable to humans (primarily milk and meat production). The culminating activity presents a case study in which students consider the consequences of losing the naturally selected attributes of breeds less adapted to domestication.

Students should already be familiar with the concepts of evolutionary adaptation, natural selection, and DNA/genetic engineering.

SUBJECT MATTER: Biology/ Living Environment


Students will be able to:

  • Describe the traits of cows that make them suitable for domestication.
  • Explain how the cow’s digestive system has adapted to its environment.
  • Compare and contrast natural and artificial selection.
  • Describe various breeds of selectively bred cattle and their desirable traits.
  • Discuss some limitations and negative consequences of selective breeding.


From the National Science Standards for Science Content, Grades 9-12.

As a result of activities in grades 9-12 students should develop understandings of:

Biological Evolution

  • Species evolve over time. Evolution is the consequence of the interactions of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection by the environment of those offspring better able to survive and leave offspring.
  • The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms.
  • Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms.

Behavior of Organisms

  • Like other aspects of an organism’s biology, behaviors have evolved through natural selection. Behaviors often have an adaptive logic when viewed in terms of evolutionary principles.

New York State Core Curriculum Alignments
From the Living Environment Core Curriculum.

STANDARD 4: Students will understand and apply scientific principles and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

Key Idea 2: Organisms inherit genetic information in a variety of ways that result in continuity of structure and function between parents and offspring.

Performance Indicator 2.2: Explain how technology of genetic engineering allows for human to alter genetic makeup of organisms.

2.2a: For thousands of years new varieties of cultivated plants and domestic animals have resulted from selective breeding for particular traits.

2.2b: In recent years new varieties of farm plant and animals have been engineered by manipulating their genetic instructions to produce new characteristics.

Key Idea 3: Individuals and species change over time.

Performance Indictor 3.1: Explain the mechanisms and patterns of evolution.

3.1e: Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life-forms as well as for the molecular and structural similarities observed among the diverse species of living organisms.

3.1f: Species evolve over time. Evolution is the consequence of the Interaction of (1) the potential for a species to increase its numbers… (4) the ensuring selection by the environment of those better able to survive…

3.1j: Behaviors have evolved through natural selection. The broad patterns of behaviors exhibited by organisms are those that have resulted in greater reproductive success.

3.1k: Evolution does not necessitate a long-term progress in some set direction. Evolutionary changes appear to be like the growth of a bush: Some branches survive from the beginning with little or no change, many die out altogether, and others branch repeatedly, sometimes giving rise to more complex organisms.



NATURE, Holy Cow, selected segments:

Clip 1, “A Cow’s Digestive System”

Clip 2, “Desirable Breeding Traits in Cattle”

Clip 3, “Different Breeds of Cattle”

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Web sites

Breeds of Livestock
An Oklahoma State University Web site featuring photos and descriptions of various breeds of cattle from around the world.

World Climate Map
A map of the world showing different climate zones.

Genetic Engineering
A Regents’ preparatory Web site featuring a description of how the meaty English Shorthorn cow was selectively bred with the heat-resistant Brahman cow to produce the Santa Gertrudis, a hybrid which possesses the positive characteristics of both parent breeds.

Punnett Squares
An interactive Web-site which explains how Punnett squares can be used to determine the likelihood that certain traits will be passed on to future generations.

A Dying Breed
A New York Times article which discusses the pros and cons of increasing hybridization by Bahiman cattle ranchers in Uganda of their native Ankole cattle with Holstein cattle from the United States.


For each student:

  • “Traits of Ankole and Holstein Cattle” Student Organizer (PDF)(RTF)

For each group:

  • “Man’s Best Friend?” Student Organizer (PDF)(RTF)
  • “Cattle Breeding” Student Organizer (PDF)(RTF)
  • “Finding the Balance” Student Organizer (PDF)(RTF)

For the class:

  • “Traits of Ankole and Holstein Cattle” Student Organizer Answer Key (PDF)(RTF)
  • “Man’s Best Friend?” Student Organizer Answer Key (PDF)(RTF)
  • “Cattle Breeding” Student Organizer Answer Key (PDF)(RTF)
  • “Finding the Balance” Student Organizer Answer Key (PDF)(RTF)
  • Computer with Internet access, projector, and screen


Prior to teaching this lesson, you will need to:

Preview all of the video clips and Web sites used in the lesson.

Download the video clips used in the lesson to your classroom computer, or prepare to watch them using your classroom’s Internet connection.

Bookmark the Web sites used in the lesson on each computer in your classroom. Using a social bookmarking tool such as or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Next: Proceed to Activities.

  • bob

    This doesn’t have a bibliography!

  • Mandii

    eating cows is WRONG!!!

  • Kaler

    I love cow meat.
    It tastes good in my mouth.

  • chloe

    bobs right it needs to have a biblyography

  • jordon

    i like cow meat but i think it is sick the wat they treat the cattle to produce the meat :)

  • Jordon

    why do poultry staff hav 2 treat them like dat they have lives 2 live like us :(

  • Eat Steak!

    cows are delicious, but if they are cloned for too long then they will eventually all die out. we will be without milk! OH NOES!

  • frank c. robson

    Excellent history of the cow and the benefits to mankind. Should be shown so that all of society,whether you live in a large metropolitan area or medium sized community knows where our meat,milk,byproducts come from. In addition the cow produces from vegetation in area remote which cannot be used for any other purpose.

  • Gillian

    Thanks for a great lesson plan on teaching about natural selection with something other than dogs!


    i love to eat cows raw…. but im satanic…so?

  • C Kohn

    As an agricultural instructor and as a cattle producer, I can assure you that in the vast majority of cases, cattle are treated as well as they can be. This isn’t just because a producer should do it (and are trained to do so by law) – they also have an economic incentive. An abused animal is not a producing animal, and meat and milk production are the first things to be affected by an abused animal. If a producer is going to make a profit, they must make every effort to ensure every physiological need of their animal is met, from water and nutrients to health and wellbeing to even sunlight and psychology. Yes, there are bad apples in the ag industry, just like any industry, but the vast majority of producers care about their animals, their land, and their consumer.

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