1. Summary:

he video discusses the fact that whales at one point in time were able to walk on land and thus, evolution has bred out whales having legs to better adapt to their environments. The video is based on a revolving theme that whales and humans have evolved from an ancient, four-legged walking land animal. The video goes on to prove this by looking at different forms of where we can get such evidence.


2. Why watch this video?

1. Have you ever wondered …?
How they class different animals together like whales?


2. Would you like to know how [something works or happens/ happened]?
Whales have blowholes instead of gills?


3. Have you ever been confused by …?
The fact that whales from the fossil record would have needed legs?


3. Key terms:

Term Definition
Evolution Evolution is when a species undergoes physiological changes to its internal and external body in order to better survive in a certain environment that is present. It’s the change over a long period of time on the characteristics and biology of a species.
Embryology This is the study and examination of the biology of reproductive development of species and how some species when in prenatal development share similarities in anatomy. It can be used to compare different species and explain why some of the same species evolve differently overtime.
Fossil Record The fossil record is essentially a data base where we are able to collect data and verify proof of past species that once roamed Earth. It is where we can find fossils or remains of species and rocks so we can further predict when or what dates certain populations have been around, and what they might have looked like.


4. Loose ends: 

Loose end #1:

A human embryo and dolphin embryo look similar, but why do the leg buds stop growing in a dolphin embryo?

The reason as to why evolution has bred out legs in whales and dolphins is because these animals started to transition and spend most time in a watered ecosystem. However, the physiological process that prevents the arm buds and leg buds from forming in whale species is due to a gene called Sonic hedgehog. Sonic hedgehog only functions in the first quarter of gestation. This is what forms everything beyond the elbow such as wrists, fingers, etc. Therefore, this would explain why whales today still contain hip bones. Nowadays we see dolphin’s without hip bones, and this is because a gene called Hand2 inactivates sonic hedgehog all together and causes limb development to cease.

Loose end #2:

What made human’s and whales (mammals) evolve differently despite having a common ancestor?

We all share 23 proteins, and overtime through the evolutionary process, our cells and DNA continually kept on replicating, and causing the translation of DNA to proteins. The reason for our cells and DNA changing is due to the environmental and climatic stressors that the species has had to adapt to in order to survive. The process of natural selection takes place, which causes mutations in our genes and DNA thus altering our appearance and physiological processes due to different environments. Even though humans and whales have evolved from a common ancestor, we have evolved independently of one another due to the environment that we were able to survive best in.

Loose end #3:

If all things are related, then what is the ancient four-legged land animal that whales are related to?

Pakicetus is known as the closely related ancestor to the modern whales that we know today due to evidence in the fossil record. Plakicetuswas around over 50 Million years ago and had the closest characteristics to that of our whales today. These were land animals that had a similar long skull especially in the ear regions which were surrounded by bony walls.


5. Self-Test Questions:

Question 1

Question: Which of the following is NOT a cetacean?
Answer a: Whale
Answer b: Hippopotamus
Answer c: Porpoise
Answer d: Dolphin
What’s the answer and why?
(b) Hippopotamus: Because they are from the group of Anthracotheres, and evolved separately from different groups than whales, but are the closest relatives to whales.

Question 2

Question: What do whales typically do or have that fish don’t?
Answer a: They provide milk to feed their young
Answer b: They are warm blooded just like humans
Answer c: Whales do not have gills like fish do, instead, they breathe through a blowhole that lies on the top of their heads to supply oxygen to their lungs
Answer d: All of the above
What’s the answer and why?
(d) All of the above: Because whales are mammals and they typically have similar functions to other mammals such as producing milk as food for young, being warm blooded like humans and other land mammals and breathing with lungs instead of gills.

Question 3

Question: What are different things to look at to prove evolution exists?
Answer a: Pictures of past species, and embryology and development
Answer b: DNA comparisons, and the news/newspaper
Answer c: Comparative anatomy, and the fossil record
Answer d: Reading Wikipedia and other online reading forums
What’s the answer and why?
(c) Comparative anatomy and the fossil record: Because pictures are never solid proof of evidence for things as they can always be altered, and you should never rely on social media forms to give factual proof as those can be bias.

Question 4

Question: When did the Basilosaurus whale live to the end of?
Answer a: Archean Eon (4000 Ma to 2500 Ma)
Answer b: Phanerozoic Eon of the Cenozoic Era (66 Ma to today)
Answer c: Proterozoic Eon of the Mesoproterozoic Era (1600 Ma to 1000 Ma)
Answer d: Phanerozoic Eon to the Mesozoic Era (542 Ma to 252 Ma)
What’s the answer and why?
(b) Phanerozoic Eon of the Cenozoic Era (66 Ma to today): Because the Basilosauraus lived ~34-40 Million years ago, which would be within the time frame from the Cenozoic Era to today, because the Cenozoic Era started around 66 Ma.

Question 5

Question: What is the name of the “walking whale?”
Answer a: Maiacetus
Answer b: Basilosaurus
Answer c: Indohyus
Answer d: Pakicetus
What’s the answer and why?
(a) Maiacetus: Because Basilosaurus had too small/short of legs capable to walk, and the Maiacetus whales had longer legs with more complex/stronger legs and webbed feet to be able to walk on land and swim.

Shared by: Lindsey Buhay (llb336)

Item Credit: Stated Clearly

Reuse License: YouTube Standard License

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