Evolution Analysis of Hippopotamus and Crocodile

Hippopotamus Amphibius
(Hippopotamus)

Variation

Differences between the Common Hippo
and the Pygmy Hippo

 Different Colors – Pygmy Hippo is darker and common hippo is lighter.
 Pygmy are significantly smaller.
 Features like nose and eyes and ears are more prominent on the common hippo and the nostrils are on the top of its head.
 Common hippo has a larger head.
 Pygmy has a longer neck.
 Pygmy has longer legs.
 Pygmy skin is shiny and smooth; Common’s skin is rough.
 The common hippo has webbed feet.
 Common Hippo has many more, sharp teeth than the pygmy hippo does (not seen in picture).

Variation is a species is the first of the four premises of Natural Selection. There needs to be variation in a species for Natural Selection to occur. For example, the variation could be the height of trees. If there are very large trees and very short trees in the same species, one will likely be “fitter” than the other meaning its height (or another trait) allows it to survive better. The trees vary in size because different alleles exist. The tall trees have two tall alleles, or one tall and one short, and the short trees must have two short alleles. In terms of natural selection, the tall trees in this case would be more fit because they absorb the sun directly. The small trees get covered by the bigger ones, so they obtain less sunlight. Eventually, because of the lack of sunlight received, the short trees which carry the short alleles will die off. Eventually there will only be tall trees, because all the short and the short alleles died off, leaving the tall trees to survive and reproduce. This example directly illuminates the importance of variation in a species for natural selection; without variation the other steps cannot occur, because every individual is the same.

Adaptation

The common Hippo lives all over the continent of Africa, but are more common in the eastern part of the continent. They like to live near water specifically lakes, ponds, or swamps. They think shallow waters, but that are big enough to submerge their whole body underwater. They like water that doesn’t move much and has a soft bottom. The hippo lives in water mostly during the day, where it is cool, and in grasslands in the night where they eat grass.

Positive Adaptations and Description
• 1. Nostrils on the top of the head
• 2. Webbed Feet
• 3. Size
• 4. Muddy Color
• 5. Prominent Eyes
• 6. Short legs and neck

• 1. The nostrils being on the top of the head allow the hippo to remain underwater whilst breathing.
• 2. Webbed feet allow the hippo to move through the water more efficiently.
• 3. The size of the hippo is good for scaring off and intimidating other animals.
• 4. The color of the common hippo likely allows it to blend in with the water it submerges in (camouflage).
• 5. The prominent eyes allow the hippo to stay submerged and be able to see above water.
• 6. The short legs and neck are likely beneficial for the hippo so it doesn’t take up too much more space, and so it can fit comfortably in the water it desires.

Negative Characteristics and Description

1. Size

2. Webbed Feet

3. Eyes on top of head

4. The size of the hippo may inhibit its movement on land and prevent him from escaping potential predators.

5. Webbed feet not adapted well for movement on land.

6. The location of the eyes may also be detrimental because the hippo can’t see below it easily.

As far as natural selection goes, survival is determined by the traits an individual has. Well adapted traits will help an individual survive. If we look at the hippo for example, the nostrils on the top of its head are a good trait that allow it to breathe while its body is submerged in the water. If the nostrils are on the side of its head, it would prevent this from happening, so it would have to rise up to breathe. This is an example of a trait that is not adapted to the environment. This negative trait would make the hippo more visible to predators as a large animal like this cannot go unseen while moving (it would need to move to breathe). In terms of natural selection, the hippo with the negative trait will die and its trait will die with it, so it cannot reproduce any more, and thus isn’t creating any more hippos with nostrils on the side of their head. The Hippo that has adapted will survive because it doesn’t have to move to breathe, so it will be unseen thus surviving. This hippo, that is well adapted, will go on and reproduce creating more hippos similar to it.

Crocodylinae (Crocodile)

Positive characteristics and description shared by the crocodile and hippopotamus

1. Many large sharp teeth

2. Muddy color

3. Eyes atop head

4. Large Size

5. Helps eat food although they eat different foods (hippo is herbivorous and crocodile is carnivorous)

6. Helps them both hide from other animals.

7. To help both of them see while staying submerged under water.

8. The large size helps them both intimidate other organisms.

The crocodile and hippopotamus are two of the largest and most feared organisms that coexist in Africa today. They share many characteristics, such as large teeth and eyes atop their heads, because of the environment they live in. They both live a majority of their days in the water, be that of a pond or swamp or lake. They need to have eyes on their head which help the stay hidden. If they didn’t have their eyes in this location, it’s safe to say they wouldn’t survive (because prey or predators can see them, so they couldn’t get food or they would be food). Also, they need many large, sharp teeth to rip apart their food. Without these teeth, they couldn’t survive, because they couldn’t eat.

Natural selection is a process that takes many, many years and generations. It begins in a species that has individuals with genetic variation, likely caused by mutations, either beneficial or harmful. Then comes overpopulation. Individuals have more offspring than the environment and ecosystem can support. Next, competition occurs. Not all of the individuals can survive like previously mentioned, so those with better traits will out-compete the individuals without that trait. Finally, those best adapted, with beneficial traits, will survive and reproduce. The others, with poorly adapted traits, will die along with their bad traits. Eventually, the population will be cleansed of the bad trait, and all of the individuals will have the good trait. In terms of the hippo, there was likely another type of hippo, one that may have had smaller teeth. Eventually, a mutation may have occurred where the teeth were larger. With outside influences, the environment might have changed where small teeth couldn’t rip apart a new type of plant. Over time, there was likely too many hippos that some had to die. The hippos with larger teeth could rip apart and chew the new plant, thus feeding themselves. Those with small teeth died because they couldn’t eat. Finally, there were much more hippos, and eventually all the small teeth would die off. All new hippos being born had to have parents that survived, so all hippos were those with large teeth.

Works Cited
Bio Expedition. “Common Hippopotamus.” Hippopotamus Facts and Information, www.hippoworlds.com/common-hippopotamus/. Accessed 7 May 2017.
San Diego Zoo Global. “Pygmy Hippopotamus.” San Diego Zoo Global Animals and Plants, animals.sandiegozoo.org/animals/pygmy-hippopotamus. Accessed 7 May 2017.