Introduction to Evolutionary Biology

We've explored how landforms change over time - from plate tectonics to weathering, erosion, and deposition. We looked at the geologic time scale and how scientists figured out the age of the Earth. Now, we'll focus on how life has changed over time.

Within the following reading are tasks for you to do. Please do these in your science notebook.

Task 1: Read the following and create a Venn diagram showing similarities and differences between unicellular and multicellular organisms.

Unicellular organisms were the first living organisms on Earth. There were tons of types, but they were each made of only one cell that did EVERYTHING. Unicellular life first appeared 3.8 billion years ago! Most life on Earth is still unicellular. We'll talk more about these unicellular organisms in the next unit.

A unicellular organism

Multicellular organisms are first evident in the fossil record 1.2 billion years ago. At first life was restricted to the oceans and other bodies of water. In multicellular organisms, different cells have different jobs. Cells are organized into tissues which make up organs which make organ systems which make...organisms. Tiny seaweeds were the first multicellular organisms. The first animals were kind of like today's jellyfish.

Organization in multicellular organisms.

All life needs water, energy, materials, and space to live.
Life moved out of water about 500 million years ago. To move out of the water, life had to develop structures to get water - like roots in plants. Fungi evolved that could absorb water from its surroundings.
Scientists think insects were next, followed by amphibians and reptiles, then mammals and birds.

Task 2: List the two mass extinctions and one fact about it.

We discussed mass extinctions during the Geologic Time Scale Gallery Walk - but let's review. Mass extinctions are when MANY life forms die out in a short time period. Two major mass extinctions are evident in Earth's past.
After the Permian, 90% of all living species died out. Scientists believe this is because all the continents were in a supercontinent (PANGEA!) which changed the climate.
After the Cretaceous a giant asteroid hit the Earth changing the climate and causing other catastrophes (tsunamis) that wiped out many living organisms (dinosaurs).
Mass extinctions allow different species to diversify.

Task 3: List 3 scientists who led the way to understanding how life changes over time.

Lamarck

In the early 1800s, Jean Baptiste de Lamarck noted that fossils seemed to show change over time. He thought that if a giraffe stretched its neck to reach leaves it's neck would get longer during one lifetime and pass its stretched neck down to its offspring. He had no evidence to support this.

Simultaneously, Gregor Mendel was studying traits of peas and how traits could be passed on. People did not take his ideas seriously because they went against the most common ideas about inheritance of the day.

Charles Darwin voyaged on the HMS Beagle and observed the diversity of life, especially on islands. This led to him developing the theory of evolution by natural selection.


Task 4:
1) Write this in your notebook: Evolution by natural selection is a scientifically accepted _____________.
2) List 3 types of evidence for evolution by natural selection.

Today, evolution by natural selection is a scientifically accepted theory. There is a lot of evidence for it. This includes fossil evidence, embryological evidence, and DNA evidence. We'll talk more about these later.




Task 5: Watch the video focusing on one part of cells dividing. How do you think variation occurs in living organisms? We'll discuss this more in class. Don't be afraid to be wrong. Just write something :-).

Task 6: Define the following in the back of your science notebook. This unit is called "Geology and Evolutionary Biology".

Evolution: the process through which species change over time, this change is due to genetic variations that are passed down
Natural selection: some traits help species survive long enough to successfully reproduce, overtime that trait becomes more common in a species
Adaptation: any inherited trait that gives an organism an advantage in its particular environment
Speciation: the evolution of a new species from an existing species

When you finish this, please work on the geology review materials or missing work.

Happy Monday!

Ms. Nickel

Source: Textbook (McDougal Littell Science Grade 8, Unit B, chapter 1)