History of Life

Objective

To familiarize students with the major kinds of organisms discussed in the lecture class on "History of Life".

To familiarize students with the concept of geologic time and to give students an understanding (and appreciation) of how long ago each of the major events in the history of life occurred. 

Part 1. Kinds of Organisms

The purpose of this exercise is to familiarize students with the major kinds of organisms that are found on earth. The discussion of earth's history that follows will refer to these kinds of organisms.

Many taxonomists categorize organisms into 3 domains: Bacteria, Archaea, and Eukarya. The Bacteria and Archaea are procaryotes. The domain Eukarya includes the eucaryotes. It is composed of these kingdoms: Protists, Fungi, Plants, and Animals.

In the exercise below, you will examine specimens from each of the groups that are listed. You will also be asked to draw representatives of each group. Along with your drawings, you should include descriptions where necessary. For microscopic organisms, write the magnification used next to your drawing. For larger organisms, write the length of the organism. These drawings, descriptions, and measurements will be helpful when studying for quizzes.

During the next lab quiz, you will be shown organisms and asked to name the group that it belongs to.

Procaryotes

The exercises below require the use of a microscope. Click here for instructions on using the microscope.

Procaryotes are single-celled organisms and the cells are the simplest kind of cells. They belong to the domain Archaea or Bacteria (see the diagram above).

1. Examine a slide of bacteria (suggested slides: typical bacillus or typical spirillum) under high power (430 X). The bacillus cells are often attached end-to-end forming a long, threadlike structure. Draw a bacillus or spirillum cell below. Write the name of the slide next to your diagram. 

2. Cyanobacteria are photosynthetic procaryotes and may be connected in chains or filaments. Examine a slide of a cyanobacterium (example: Anabaena) under high power (430X). Draw representative cyanobacteria below.

Protists

Protists, fungi, plants, and animals are called eucaryotes. The cells of these organisms are complex. Unlike procaryotes, the cells of eucaryotes contain many membrane-bound (surrounded by membrane) organelles.

Protists may be multicellular but their structure is simpler than plants or animals. For example, they lack the tissues that are found in plants or animals.

3. Examine and draw a single-celled protist such as Paramecium or Amoeba. Record its name and the magnification used for viewing.

4. Examine and draw a representative alga such as Fucus. Record its name and the length of the organism.

Fungi

Fungi are immotile (cannot move). Fungi do not make their own organic food like plants do. Instead, they must obtain it from their environment.

5. Examine representative fungi on display and draw one below. Be sure to include the name and a scale or measurement.

Animals

Invertebrates

Invertebrates is a general word that is used to refers to all animals without a backbone. The largest group of invertebrate animals is insects. We will learn the various kinds of invertebrates in later classes.

Vertebrates

Vertebrates are animals that have a backbone. There are five groups of vertebrates: fish, amphibians (frogs, salamanders, etc.), reptiles (snakes, lizards, etc.), birds, and mammals.

Examine representative vertebrate animals on display. Make drawings or describe each of these kinds of animals below. Your drawings or descriptions should be sufficient to allow you to study for a quiz.

6. fish

7. amphibians

8. reptiles

9. birds

10. mammals

Plants

The earliest plants did not produce seeds. There are two groups of seed plants. Gymnosperms are seed plants that do not have flowers. Angiosperms are flowering plants. 

Seedless Plants

11. Examine the representative seedless plants on display (example: ferns or mosses). Mosses can also be seen in either of the terrariums. Draw at least one of these in the space below. Include its name and size.

Gymnosperms

Gymnosperms are seed plants that do not produce flowers. They include our evergreen trees such as pine, spruce, hemlock, etc.

12. Examine parts from representative gymnosperms plants on display. Draw some of these structures in the space below. Include the name of the organism and the size of the part.

Angiosperms

Angiosperms are flowering plants. Most of the plants that we are familiar with are flowering plants. Some examples are most deciduous trees (not evergreen), grass, shrubs, herbs, etc.

13. Examine parts from representative angiosperms plants on display. Draw some of these structures in the space below. Include the name of the organism and the size of the part.

Part 2. Time

This exercise is designed to help students understand the geologic time scale by constructing a timeline. Major events in the evolutionary history of life will be placed on the line (see the diagram below). The distance between these events will be proportional to the amount of time that passed between the events.

The timeline in the diagram below is too short to be able to include more recent evolutionary events, so we will create a longer one.

In the hall outside the biology room, measure a distance on the floor to represent the amount of time that has passed since the formation of the earth 4.6 billion years ago. One centimeter on this timeline will represent one million years. 

Mark each end of the line with a piece of tape. One end of the tape should be folded back so that the sticky surface is covered. This will facilitate its removal from the floor.

Because 1 centimeter = 1 million years, your line should be 46 meters long. The tape at one end of this line represents today, the other end represents the time when the earth was formed.

Time Periods

At one end of the hall, use a piece of tape to represent today. Write the word "today" on the tape.

Use tape to mark each of the following periods. 

The beginning of the Cenozoic - 66 mya (million years ago) - The edge of the tape should be 66 cm from "today."

The beginning of the Mesozoic - 245 mya - This mark should be 245 cm (2.45 m) from "today."

The beginning of the Paleozoic - 570 mya

Notice that all of the marks above are less than 6 meters from the mark representing today.

The timeline is now divided into the four major geologic eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic. The Precambrian is the longest of these four time intervals and the Cenozoic is the shortest.

14. How many times longer is the Precambrian than the Cenozoic? [Hint: Precambrian = 4030 million years]

15. How many times longer is the Paleozoic than the Cenozoic?

16. How many times longer is the Mesozoic than the Cenozoic? 

Organisms

The diagram below shows evolutionary relationships among the major groups of organisms. Use this diagram as a reference as you construct your timeline.

Each item below that has a date (either mya or bya) should be marked on the timeline with a piece of tape. The beginning of the Paleozoic, Mesozoic, and Cenozoic has already been marked.

Precambrian

The oldest fossils on earth are 3.6 billion years old (3600 mya). These organisms are procaryotes (simple, single-celled organisms such as bacteria).

The first eucaryotes appeared 1.5 bya (1500 mya).

The first multicellular organisms arose 650 mya.

The first animals evolved 600 mya.

Paleozoic

The Paleozoic began 570 mya with the evolution of hard parts such as bones and shells that were capable of producing abundant fossils.

Plants evolved and became common. They expanded into terrestrial environments 400 mya. 

Our fossil fuels (coal, oil, natural gas) came from the remains of dense forests of club mosses, horsetails, and ferns (seedless plants) that were common 300 mya.

Marine invertebrates were common at the beginning of this era. Next came the first vertebrates (fish) (400 mya) followed by amphibians, then reptiles. 

Insects evolved during this period.

The Paleozoic ended when all of the continents on earth drifted together forming a large continent called Pangaea. The loss of habitat and increased competition associated with the formation of Pangaea caused massive extinctions.

Mesozoic

The Mesozoic began 245 mya.

Gymnosperms (plants with seeds but no fruits, example: evergreen trees with needles) became abundant by the beginning of the mesozoic 245 mya.

The first flowering plants (angiosperms) appeared 144 mya but did not become dominant until the Cenozoic.

Reptiles were dominant during the Mesozoic. Dinosaurs (a type of reptile) evolved during the Mesozoic 245 mya. 

The first birds and mammals appeared. Mammals remained small and insignificant while the dinosaurs were dominant. The extinction of the dinosaurs at the end of the Mesozoic (66 mya) led to the diversification of mammals in the Cenozoic.

Cenozoic

The Cenozoic follows the extinction of the dinosaurs 66 mya.

There was an abundance of birds, mammals, and insects during the Cenozoic. Angiosperms (flowering plants) became the dominant type of plant during the Cenozoic (66 mya).

Hominids (ancestors of humans) appeared about 3 mya.

The earliest humans (Cro-Magnon) evolved approximately 100,000 years ago.

Human recorded history is less than 5,000 years old.

The length of the timeline that represents human recorded history (0.05 mm = 50 um) is about the size of a single eucaryotic cell. It is too small to see with your eye.

If human recorded history were 1 inch on a timeline, the rest of the timeline would be 16 miles long.

Summary

Your timeline should have the events listed below.

Event	MYA (million years ago)
Human recorded history (5,000 yrs)	0.005
Earliest humans (Cro-Magnon)	0.1
Hominids (ancestors of humans)	3
Beginning of the Cenozoic Extinction of the Dinosaurs Angiosperms became dominant	66
First Angiosperms	144
First dinosaurs and mammals	245
Gymnosperms became abundant	245
Beginning of the Mesozoic Pangaea formed Mass extinctions occurred	245
Forests that formed fossil fuels (coal and oil)	300
First vertebrates (fish)	400
Seedless land plants become common	400
Beginning of the Paleozoic Evolution of hard parts	570
First animals	600
First multicellular organisms	650
First eucaryotes	1500
Oldest fossils	3600
Formation of the earth	4600

Part 3. Fossils

Representative fossils from the Precambrian, Paleozoic, Mesozoic, and Cenozoic are on display.

Note – The fossils on display are extremely expensive. Please handle them with care and return them to their proper container.

Precambrian

The oldest fossils are procaryotes that date approximately 3.5 billion years ago. Protists (the first eucaryotes) arose during this time period.

The first animals arose near the end of this period. They did not have hard skeletal material.  Examine and draw the fossil of Spriggina, a segmented worm that lived near the end of the Precambrian.

Paleozoic

The number of different kinds of organisms increased dramatically during the Paleozoic.

Invertebrates

Examine and draw a representative fossil of each of the invertebrates groups listed below:

Vertebrates

Fish, Amphibians and Reptiles also evolved during this period.

Plants

Seedless plants evolved and became dominant. Note the seed fern

Mesozoic

Click here for an answer sheet.