If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Activity: How Closely Related Are We?

Purpose

This activity will help you understand the relationship between different species, and show you how we (humans) are related to other species. The evolution of life from bacteria to humans is pretty hard to wrap your mind around, and showing connections among different species will increase your understanding.
A fruit fly, "Drosophila repleta lateral" by Bbski - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0-2.5-2.0-1.0 via Wikimedia Commons

Process

One of the amazing things about life is just how interconnected living things are. Genetic studies have helped biologists pin down the extent of these connections. In this activity you will be asked to consider what you know about these relationships.
Look at the How Closely Related Are We? Worksheet and try to match the list of organisms with the percentage of DNA shared with humans.
Once you have done this, take a look at the answer key, and see how well you did.

For Further Discussion

Some people find it surprising that chimps and zebrafish have so much DNA in common. What are some of the physical traits they share? Post your thoughts to the Questions Area below.

Want to join the conversation?

  • aqualine ultimate style avatar for user Yellow Top White Knot
    They share eyes, mouths, teeth, bones, tail-bones, rectums, spines,
    (6 votes)
    Default Khan Academy avatar avatar for user
  • leafers seed style avatar for user Alex Harper
    they both have a way to move around
    (4 votes)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user frew.wilmot
    They both have to eat and they can reproduce. They have eyes, noses, and mouths. They also both have digestive systems. That's about all I can think of.
    (3 votes)
    Default Khan Academy avatar avatar for user
  • marcimus pink style avatar for user jaydes18
    say if the mother or father has blue eyes and red hair and the daughter has brown eyes and black hair how does this happen?
    (2 votes)
    Default Khan Academy avatar avatar for user
    • leafers seedling style avatar for user 2891112
      The issue of inheritance of traits and genetics include change, combinations of genes, and random chance. Otherwise, we would all be duplicates of one parent.
      As for the daughter with eye and hair color, there are various possibilities:
      1. The genes for eye color and hair color possess dominance and recessiveness, so maybe both mother and father had recessive genes for brown eyes and black hair, while they may have dominant genes for blue eyes and red hair. So both parents have genes (blue+brown) for eyes, and dominant blue for eyes wins out, so the parents have blue eyes, and have genes (red+black) for hair, and the dominant red for hair wins out, so both parents have red hair. The sperm and egg only have half the genes, so the father can produce sperm with only blue-genes for eyes or only brown-genes for eyes, but not both, and the same goes for the mother producing eggs with only blue-genes or only brown-genes. Same goes for the hair genes. Therefore, the daughter may have been conceived with a (brown eyes, black hair) sperm and a (brown eyes, black hair) egg to get both (brown-brown) genes for eyes, with no dominating blue gene for the eyes, and both (black-black) genes for hair, with no dominating red gene for the hair.
      2. There may not be genes for dominance-recessiveness, since it depends on the trait, but genes can blend or cross-over, so maybe the brown-eye gene was formed from parts of the eye genes from both parents, and the part for blue-eyes did not collect together, with only parts for brown eyes blending and collecting to form the daughter's genes.
      3. Multiple genes cause a trait, so the daughter got a combination of two or more genes that made brown eyes, which was a different combination than the parents had.
      4. Mutation ... by some random chance, a gene was not properly copied, leaving out the genes for blue eyes, or radiation randomly hit a gene changing the A nucleotide to T or something like that, changing the blue-eye gene to a brown-eye gene.
      See http://en.wikipedia.org/wiki/Mendelian_inheritance and note the discussion of Punnett Squares for how recessive traits can show up in children but not in their parents.
      (2 votes)
  • leaf blue style avatar for user 17sintyl
    They both produce energy
    (1 vote)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user Dawn
    when a red eye female and white eyed male mix why are there no white eyed offspring
    (1 vote)
    Default Khan Academy avatar avatar for user
  • leaf green style avatar for user gbalatra503
    What do you think the primordial species was like?
    (1 vote)
    Default Khan Academy avatar avatar for user
  • leaf blue style avatar for user MargaretWMerritt
    It seems strange to share so much DNA with a zebrafish. How does that work?
    (1 vote)
    Default Khan Academy avatar avatar for user
    • leafers seedling style avatar for user 2891112
      The issue of inheritance of traits and genetics include change, combinations of genes, and random chance. Otherwise, we would all be duplicates of one parent.
      As for the daughter with eye and hair color, there are various possibilities:
      1. The genes for eye color and hair color possess dominance and recessiveness, so maybe both mother and father had recessive genes for brown eyes and black hair, while they may have dominant genes for blue eyes and red hair. So both parents have genes (blue+brown) for eyes, and dominant blue for eyes wins out, so the parents have blue eyes, and have genes (red+black) for hair, and the dominant red for hair wins out, so both parents have red hair. The sperm and egg only have half the genes, so the father can produce sperm with only blue-genes for eyes or only brown-genes for eyes, but not both, and the same goes for the mother producing eggs with only blue-genes or only brown-genes. Same goes for the hair genes. Therefore, the daughter may have been conceived with a (brown eyes, black hair) sperm and a (brown eyes, black hair) egg to get both (brown-brown) genes for eyes, with no dominating blue gene for the eyes, and both (black-black) genes for hair, with no dominating red gene for the hair.
      2. There may not be genes for dominance-recessiveness, since it depends on the trait, but genes can blend or cross-over, so maybe the brown-eye gene was formed from parts of the eye genes from both parents, and the part for blue-eyes did not collect together, with only parts for brown eyes blending and collecting to form the daughter's genes.
      3. Multiple genes cause a trait, so the daughter got a combination of two or more genes that made brown eyes, which was a different combination than the parents had.
      4. Mutation ... by some random chance, a gene was not properly copied, leaving out the genes for blue eyes, or radiation randomly hit a gene changing the A nucleotide to T or something like that, changing the blue-eye gene to a brown-eye gene.
      See http://en.wikipedia.org/wiki/Mendelian_inheritance and note the discussion of Punnett Squares for how recessive traits can show up in children but not in their parents.
      (1 vote)
  • piceratops seed style avatar for user 17dithan
    They both have a backbone.
    (1 vote)
    Default Khan Academy avatar avatar for user
  • leafers seed style avatar for user 17wildyl
    They both produce energy.
    (1 vote)
    Default Khan Academy avatar avatar for user