Life on Earth Worksheet Essay
Life on Earth Worksheet
Taxa to explore – Elephants.
1. Review terms (write definitions for these terms)
Species, families, or groups still in existence
Species, families, or groups no longer in existence, end or died out Genotype
Genetic make-up of an organism
Physical attributes of an organism, observable or measurable traits Synapomorphy
Shared characteristic that are inherited from most recent common ancestor
Background: There are three extant species of elephant: Elaphas maximus (Asian elephants), Loxodonta africana (African elephants), and Loxodonta cyclotis (African forest elephants). Their taxonomic hierarchy is as follows:
2. Collect an image of each species. You will submit these as a part of your assignment. (see full assignment instructions)
3. Looking at these pictures, can you think of any EXTINCT animal or animals that might be a close relative of modern elephants? List it/them below. If you know the scientific name (genus and species) then you can put that. If you aren’t quite sure, just give the common name.
4. Now think about EXTANT taxa. Identify 2 animals that you might expect to be the closest LIVING relative to the elephants. List it/them below. If you know the scientific name (genus and species) then you can put that. If you aren’t quite sure, just give the common name.
Possible Relative A
Possible Relative B
5. For the closest EXTANT relatives, what characteristic(s) of that animal or its habitat led you choose it as “probable closest relative”? (consider geographic location, size, anatomy, behavior etc). Be specific.
Characteristics of Animal A
Characteristics of Animal B
-found across Africa and the Middle East
-typically live in groups
-has a prominent pair of long, pointed tusk-like upper incisors -In males, the testes are permanently abdominal
-thick, wrinkled skin
-Females have two teats, one under each flipper
-teeth growing at the rear are continuously replaced throughout life
Now to the science –
Follow the link below to read about some of the extinct relatives of elephants
6. How were the phenotypes of ancient proboscideans different from those of extant elephants?
The ancient proboscideans differ from those of extant elephants because they have multiple pairs of molars and premolars, they do not possess tusks, and they retain canines on the upper jaw.
7. Based on the information in the web-site, where did the early proboscideans evolve? The early proboscideans evolved from Africa.
More derived proboscideans (not ancient, but not extant either) also had a very different geographic distribution than elephants today:
8. Which localities seem most surprising and why?
North and South America because these locations were once abundant with these animals, such as mastodons, while having most of the animals originate from the other side of the world.
9. Identify 4 synapomorphies that are shared between ALL of these extinct and extant taxa.
Incisors and molar teeth
Four column-like legs
In extant species, relationships can also be reconstructed based on DNA Think back to your best guesses of the closest EXTANT relatives of the modern elephants.
Look at the .pdf named “Afrotheria”. The phylogeny described in this paper is based on molecular data (similarities in DNA sequences)
10. Based on that phylogeny, write in the sister taxon (taxon A) to Proboscidea. Give the formal name.
Taxon A or Sirenia Proboscidea
11. Write in the taxon (taxon B) that is sister to the clade composed of (Proboscidea + Taxon A). Give formal name
Taxon B or
Taxon A Proboscidea Hyracoidea
12. Perform an internet search for these two taxa and find out their common names. What are their common names? Describe each. The common name for Sirenia is Sea Cow. Sea cows are fully aquatic, herbivorous mammals that appear fat. They have forelimbs used for steering and a tail used for paddling. The common name for Hyracoidea are hyraxes. Hyraxes are well-furred animals with short tails and have poor internal temperature regulation.
What was your thought/reaction upon discovering what these creatures are? My thought reaction was how can animals that look nothing alike be similar to an elephant if they visually look different.
Believe it or not, there are morphological (phenotypic) similarities as well as dietary and behavioral similarities between all of these taxa. BEFORE molecular data was available, scientists already suspected that these groups were closely related. The DNA evidence only helped to confirm the relationships. We’ll do more on that in a moment.
13. Search the web to find at least two non-molecular synapomorphies between each of your modern taxa and the elephants: (be specific!)
Animal #1 name
Rock Hyraxes are furry and have the soles of the feet with large, soft pads that are kept moist. Manatees have paddle like flippers and a snout.
Animal #2 name
14. Which of the features you listed are more likely to survive in the fossil record? Explain why.
Most likely to survive in the fossil record is the snout because it consists of the bones of the jaw which are very good for becoming fossils.
15. Which are less likely? Explain why.
Less likely are the fur, soft pads at the feet, and the paddle-like flippers because all are more prone to decay rapidly because of being soft structures. The flippers are also more prone to not preserving quickly therefore eaten or broken down by aerobic microbes.
Now for molecules:
To see the actual molecular data used to create the phylogeny you saw, select the .pdf named “mammoth and sea cow”.
16. Go to page 409. Dots mean the base pair (A, C, T or G) is the same as is listed in the taxon that’s at the top (this saves ink!). Now compare the sequences for the African elephant and the Asian elephant in just the top row of page 409.
How many molecular differences do you see in the sequence shown?
There are 8 molecular difference in the sequence.
How many molecular differences do you count between the African elephant and the hyrax?
There are 11 molecular differences between the African elephant and the hyrax.
17. Based on anatomy alone (without the molecular evidence), would you have guessed that the animals in photos above represented the closest living relatives of elephants? Why or why not?
Honestly, based on the anatomy alone, I would not have guessed that the animals represent close relatives of the elephants because of the physical anatomical characteristic they have. Most animals can have similar anatomy with slight differences that contribute to their survival in an environment. Initially, I thought that the animals had similar characteristics only because of natural selection and adaptation of their environment not because of their common ancestor. This shows how molecular evidence can really help in seeing what animals belong in what lineages.