Module 1: Short Answer Assignment
Instructions: Answer all 15 questions in the space below. Use complete sentences!
1. Demonstrate the steps of the scientific process using a real-world example:
2. Describe (not list) the four-stage hypothesis for the origin of life.
3. What is a biofilm? Name three places you might find a biofilm.
4. Detail the how prokaryotes, such as bacteria, reproduce?
5. How are endospores beneficial to reproduction?
6. Describe, in detail, the four main modes of nutrition in prokaryotes.
7. What differences can be observed/detailed between prokaryotes and archaea?
8. How do bacteria cause disease?
9. Describe three roles that bacteria play in our ecosystem:
10. Describe a minimum of three differences between prokaryotes and eukaryotes?
11. Describe the three modes of nutrition of protists.
12. What are the four major types of protists?
13. How can bacteria be beneficial to our health?
14. How do algae and seaweed differ?
15. Describe how multicellular organisms could have evolved from unicellular organisms.
© 2016 Pearson Education, Inc.
BSC 109
Chapter 15: The Evolution of Microbial Life
Figure 15.5. A submarine samples deep sea vents (that create an atmosphere similar to early earth) to look for prokaryotes
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Identify the sequence and timing of the major events in the evolution of early life, ending with movement of the first life onto land
Compare bacteria and archaea
Discuss ways that bacteria harm and benefit humans/ecosystems
Explain how multicellular life evolved from unicellular life
Describe and compare the four main categories of protists
Discuss the structure, function, nutrition, and reproduction of eukaryotes
Learning Outcomes
© 2016 Pearson Education, Inc.
Canada
Origin of Earth
4,600 mya
100 miles
100 million years
United States
Large, complex
multicellular organisms
600 mya
Oldest multicellular
fossils
1,200 mya
Oldest known
rocks formed
3,850 mya
Prokaryotes
3,500 mya
O2 increasing
2,700 mya
Eukaryotes
1,800 mya
Colonization of land
500 mya
Mid-Mesozoic
180 mya
Homo sapiens
0.195 mya
4,600
miles
4,000
miles
3,400
miles
2,800
miles
1,900
miles
1,100
miles
750
miles
0
miles
Kamloops
Seattle
San Francisco
San Diego
Phoenix
Oklahoma
City
St Louis
Terre Haute
Erie
Buffalo
Albany
Boston
Map
Major Events of Early Life
Figure 15.5: A map of the United States used to illustrate the distance, in time, between major events leading up to the colonization of land and the evolution of life.
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Stage 1: Synthesis of Organic Compounds
Organic compounds are molecules that contain both carbon and hydrogen
Water vapor combined with methane and ammonia in the presence of lightening led to the formation of new, organic molecules such as amino acids!
Organic molecules are what give rise to the future structures/functions of living organisms
Four-Stage Hypothesis for the Origin of Life
Figure 15.3 Shows an early experiment performed by scientists Miller and Urey to replicate the early conditions of a primordial Earth. They found that when ammonia, methane, and hydrogen mix with each other in the presence of electricity (lightening), new, organic molecules began to form.
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Once small organic molecules formed on Earth, they began to interact.
Small, individual molecules are known as monomers, but as they begin to join together they form polymers.
Amino acids link to form proteins (polypeptides)
Nucleic acids form RNA (and later, DNA)
Lipids form triglycerides and phospholipids
Sugars form molecules of starch
Stage 2: Abiotic Synthesis of Polymers
Now that we’ve formed our polymers, the next step is their isolation from the surrounding environment via the formation of some sort of membrane barrier.
Not yet a true cell because it only exhibits some of the characteristics of life
Within a confined space, certain combinations of molecules can be concentrated and interact more efficiently
Stage 3: Formation of Pre-Cells
Flow chart:
RNA monomers
Formation of short RNA polymers: simple “genes”
Assembly of a complementary RNA chain
Complementary chain servers as template of original “gene”
One defining characteristic of life is inheritance, which is based on self replicating molecules
Early cells likely stored genetic information as RNA (later DNA) which can be replicated and passed on to new generations
Step 4: Origin of Self Replicating Molecules
Figure 15.4 Demonstrates how nucleotide monomers are able to combine to form RNA polymers. These polymers can then be replicated and passed on to future generations
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Eventually pre-cells developed into “true” cells over millions of years
Prokaryotes were the first true cells to evolve
They are found wherever there is life and outnumber any other type of cell on the planet.
All prokaryotes are unicellular
Two different types of prokaryotes
Bacteria
Archaea
Prokaryotes
Figure 15.6 The orange rods are individual bacteria found on the point of a pin. Besides showing just how small prokaryotes are, this image should also help you to understand why a pin prick can lead to infection.
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Shapes
Common Shapes of Prokaryotes
Figure 15.7 shows the three most common shapes of prokaryotic cells. Spherical cells are known as cocci, rod-shaped cells are known as bacilli, and finally there are the spiral shaped prokaryotic cells
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Archaea
Extremophiles: Tend to live in environments that would kill other forms of life
Also abundant in more moderate conditions (especially oceans)
Archaea
Figures 15.16 (left), 15.15 (center) and 15.17 (right) show examples of extreme environments in which archaea can be found. On the left we have a landfill where methane-loving archaea thrive, in the center we have a deep sea vent of extremely hot, gaseous water, and on the right we can see heat loving yellow and orange colonies of archaea.
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To synthesize organic compounds, living organisms must obtain energy and carbon
Four main modes of nutrition in prokaryotes:
Photoautotrophs
Chemoautotrophs
Photoheterotrophs
Chemoheterotrophs
Prokaryotes often form symbiotic relationships with other organisms
Prokaryote Nutrition
Photoautotrophs: Use light to drive the synthesis of organic compounds from carbon dioxide
Chemoautotrophs: Extract energy from inorganic substances such as ammonia
Photoheterotrophs: Harness energy from light but must obtain carbon from an organic form
Chemoheterotrophs: Consume organic molecules for both energy and carbon
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Many bacteria are known to cause disease via the production of toxins
Exotoxin: proteins secreted by bacterial cells into their environment
Endotoxin: Chemical components on the outer surface of bacteria that cause fever, aches, septic shock, etc.
Harmful
Microbiota: Community of bacteria that live on/in our body and aid in digestion and immunity
Bioremediation: The use of bacteria to remove pollutants from water, air, or soil
Chemical Cycles: Bacteria are essential in the recycling of chemicals needed to sustain ecosystems
Beneficial
Bacterial Effect on Humans and the Environment
Can be uni- or multicellular
Most likely formed from endosymbiosis
A relationship in which one organism lives inside the cell of a host organism
Mitochondria and chloroplasts
Different cellular structure compared to prokaryotes
Nucleus
Membrane-bound organelles
Include plants, fungi, animals, and protists
Eukaryotes 1
Cell diagrams:
Eukaryotes 2
Figures 4.2 (left) and 4.3 (right) compare the structures of prokaryotic and eukaryotic cells. Eukaryotic cells have a nucleus and specialized membrane-bound organelles such as the golgi apparatus and endoplasmic reticulum that serve different functions.
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First eukaryotes to evolve from prokaryotes
“Catch All” category
Any eukaryote that isn’t a plant, animal, or fungus
Divided into four main categories
Protozoans
Slime Molds
Algae
Seaweeds
Protists
Protists that live primarily by ingesting food
Thrive in aquatic environments
Many different types
Flagellates
Amoebas
Ciliates
Apicomplexans
Protozoans
Figure 15.23 shows the diversity of protozoans. Flagellates move by means of one or more flagella, amoebas are distinguished by their flexibility and pseudopodia, ciliated are covered in thousands of hair-like cilia used for movement, and apiconplexans are parasitic protozoans that penetrate host tissues.
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Multicellular protists
Typically feed on dead plant material
Two distinct types: plasmodial and cellular slime molds
Slime Molds
Figure 15.24 (left) shows a plasmodial slime mold. It is a large mast consisting of a single, multi-nucleated cell.
Figure 15.25 (right) shows the life stages of a cellular slime mold. Cellular slime molds are made up of independently functioning cells. When food supply is low, they swarm together to form a slug like colony that functions as a single unit and produced a reproductive structure.
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Algae: protists and cyanobacteria whose photosynthesis supports food aquatic food chains.
Unicellular Algae: Dinoflagellates, diatoms, and green algae
Colonial Algae: Certain green algae
Unicellular and Colonial Algae
Figure 15.26 shows various types of algea. (a) Shows a unicellular dinoflagellate, (b) a unicellular diatom, and (c) a colonial green algae known as volvox. Each volvox colony is a hollow ball of flagellated cells. Green algae are the most closely related to plants.
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Large, multicellular marine algae
Closest relatives are unicellular algae, not plants
Classified according the pigments present in the chloroplasts
Green, Red, or Brown Algae
Seaweeds
Figure 15.27 shows the three different types of seaweeds (categorized by pigment color)
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Three modes of nutrition utilized by protists
Autotrophs: Produce their own food via photosynthesis
Heterotrophs: Acquire food by ingesting other organisms
Mixotrophs: Capable of both photosynthesis and heterotrophy
Eukaryotic Nutrition
Figure 15.22 shows protists that use the various modes of nutrition. (A) Shows an autotroph in the form of a multicellular alga, (b) shows a parasitic heterotroph known as a trypanosome, and (c) shows euglena, a mixotroph
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