English module 1: sa assignment


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.

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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


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.


Origin of Earth

4,600 mya

100 miles

100 million years

United States

Large, complex

multicellular organisms

600 mya

Oldest multicellular


1,200 mya

Oldest known

rocks formed

3,850 mya


3,500 mya

O2 increasing

2,700 mya


1,800 mya

Colonization of land

500 mya


180 mya

Homo sapiens

0.195 mya



















San Francisco

San Diego




St Louis

Terre Haute






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.


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.


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


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




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.



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



Extremophiles: Tend to live in environments that would kill other forms of life

Also abundant in more moderate conditions (especially oceans)


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.


To synthesize organic compounds, living organisms must obtain energy and carbon

Four main modes of nutrition in prokaryotes:





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


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.


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


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


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.


First eukaryotes to evolve from prokaryotes

“Catch All” category

Any eukaryote that isn’t a plant, animal, or fungus

Divided into four main categories


Slime Molds




Protists that live primarily by ingesting food

Thrive in aquatic environments

Many different types






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.


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.


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.


Large, multicellular marine algae

Closest relatives are unicellular algae, not plants

Classified according the pigments present in the chloroplasts

Green, Red, or Brown Algae


Figure 15.27 shows the three different types of seaweeds (categorized by pigment color)


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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