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Unit 1:
Ch. 1
Ch. 2
Ch. 3
Interlude A
Unit 2:
Ch. 4
Ch. 5
Ch. 6
Ch. 7
Ch. 8
Ch. 9
Interlude B
Unit 3:
Ch. 10
Ch. 11
Ch. 12
Ch. 13
Ch. 14
Ch. 15
Interlude C
Unit 4:
Ch. 16
Ch. 17
Ch. 18
Ch. 19
Interlude D
Unit 5:
Ch. 20
Ch. 21
Ch. 22
Ch. 23
Ch. 24
Ch. 25
Ch. 26
Ch. 27
Ch. 28
Ch. 29
Ch. 30
Interlude E
Unit 6:
Ch. 31
Ch. 32
Interlude F
Unit 7:
Ch. 33
Ch. 34
Ch. 35
Ch. 36
Ch. 37
Ch. 38
Interlude G

» Getting Started » A Guide to the Reading » Tying it all together

Getting Started

Below are a few questions to consider prior to reading Chapter 3. These questions will help guide your exploration and assist you in identifying some of the key concepts presented in this chapter.

  1. What can the most spectacular orchid discovery of the past 100 years teach us about biodiversity?
  2. Why are the Greek terms eu (“true”), pro (“before”) and karyote (“kernel”) important for understanding the three domains of life?
  3. If a single bacteria of E. coli, normally found in the gut of humans, was allowed to reproduce without restriction, how long would it take to produce a population of 16,000,000 bacteria?
  4. What is “red tide”, how does it affect humans, and which group of organisms is responsible for causing it?
  5. What was the evolutionary innovation that enabled plants to grow to the towering heights seen amongst the trees?
  6. Truffles, which can sell for upward of $600 per pound, are a member of which Linnaean kingdom?
  7. What percentage of the roughly 1,000,000 known animal species are members of the animal group collectively known as the insects?

A Guide to the Reading

When exploring the content in Chapter 3 for the first time, the following concepts typically give students the most difficulty. For each concept, one or more references have been identified which may help you gain a better understanding of these potentially problematic areas.

Prokaryotes vs. Eukaryotes

As learned in Chapter 2, organisms can be classified according to several schemes.  One such scheme categorizes organisms based upon the structure of their cells.  This scheme distinguishes cells based on the presence (eukaryote) or absence (prokaryote) of a compartmentalized genetic center, or nucleus. Keep in mind that despite the similarity between the term eukaryote and the domain name Eucarya, these refer to different levels of classification.  The term eukaryote can be used to describe the structure of an organism’s cells (nucleus is present), while the domain Eucarya refers to the group of organisms represented by four kingdoms, Protista, Plantae, Fungi, and Animalia). 

For more information on this concept, be sure to focus on:

  • In Section 3.2, Organisms can also be identified as prokaryotes or eukaryotes

Prokaryote Abundance

In terms of the total number of organisms occupying the biosphere, the prokaryotes definitely take the cake.  These tiny, microscopic, ancient organisms are found in nearly all locations on our planet and make up the vast majority of life.  However, most of us remain unaware of their very existence since they cannot be seen with the naked eye.   Scientists estimate there are roughly 5 x 1030 prokaryotes on earth!  Part of the reason for the success of the prokaryotes comes from their ability to reproduce quickly.  The bacteria E. coli is capable of doubling its population in as little as 20 minutes!  If left to grow overnight, a single bacterium of this species could potentially produce a population of over 16 million individuals!  Another reason for the success of the prokaryotes lies in their ability to utilize a variety of nutritional sources, acting as consumers, decomposers, and producers within a single food web.

For more information on this concept, be sure to focus on:

  • In Section 3.2, Prokaryotes represent simplicity translated into success
  • In Section 3.2, Prokaryotes exhibit unmatched diversity in methods of obtaining nutrition

The Protists – Evolution of the Eukaryote

The kingdom Protista is considered the most ancient group amongst the Eucarya domain.  As discussed in the chapter, this group is extremely diverse in terms of size, shape, and lifestyle.  As such, it is a group that has given scientists great difficulty in their attempts to determine evolutionary relationships among its members.  This struggle is illustrated by the evolutionary tree presented in Figure 3.7.  Among the major groups of protists, only the Diplomonads are generally agreed to have branched off first.  The remaining groups are all depicted to have branched off at roughly the same time, reflecting the fact that the order in which these groups evolved is still poorly understood by scientists.  One thing is for certain, however; the protists were one of the first groups to develop organelles, tiny specialized compartments.  It is believed that organelles evolved through the process of larger prokaryotic cells engulfing smaller prokaryotic cells, with the smaller, engulfed cells taking on specialized functions within the larger host cell.  While organelles lost the ability to survive as a free-living organism, the host cell would become dependant on the function carried out by the organelle, resulting in a mutual relationship between the previously separate organisms and the generation of a new species.

For more information on this concept, be sure to focus on:

  • In Section 3.3, Protists represent early stages in the evolution of the eukaryotic cell
  • Figure 3.7, The Protista

Angiosperms and Flowers

As discussed in the chapter, the development of flowers is a relatively recent evolutionary event within the plant kingdom.  Flowering plants (angiospersms) produce seeds that are characteristically surrounded by a protective tissue which may take the form of a type of fruit.  What defines an angiosperm, however, is the flower – a structure used for reproduction.  What may be confusing to understand is that a flower typically contains both male and female reproductive structures as illustrated in Figure 3.11.  Male reproductive structures take the form of the stamen, which consists of two parts: the filament and the anther.  The anther is capable of producing pollen (male gametes; analogous to sperm in humans) which can be carried either by wind or animal to a nearby flower of the same species.  The female reproductive structure, typically in the center of the flower, is called the carpel and consists of the stigma (site of pollen attachment), the style (carries pollen) and the ovary (analogous to the female egg in humans).  When pollen reaches an ovary, the result is a plant embryo which can take the form of a seed.  Since both female and male reproductive structures are present in the same flower, this means that an angiosperm is capable of “self-pollination”, or mating with itself.

For more information on this concept, be sure to focus on:

  • In Section 3.4, Angiosperms produced the world’s first flowers

The Fungi, A Group with Many Roles

As discussed in the chapter, fungi are described as playing many key roles in most ecosystems.  The ability to play different roles stems from this group’s ability to obtain nutrients and energy from a variety of sources and in a variety of ways.  Fungi are capable of serving as a decomposer in an ecosystem by feeding upon dead or dying organisms.  Their role is to return vital nutrients back to the ecosystem for use by the system’s producers.  In a similar fashion, some groups of fungi may specialize in living upon other organisms.  This relationship can either be beneficial (mutualism) or detrimental (parasitism) to the host.  Keep in mind that these relationships may or may not be based upon the supply of nutrients.  Therefore, there is no correlation between the terms decomposer, consumer, and producer and the terms mutualist and parasite

For more information on this concept, be sure to focus on:

  • Section 3.5, The Fungi: A World of Decomposers
  • In Section 3.5, Some fungi live in beneficial associations with other species

Animal Body Cavities

One of the evolutionary innovations that helped animals develop the extreme diversity displayed by this group was the formation of a complete body cavity.  The body cavity is defined as an interior space with openings at either end (mouth, anus).  The text describes two distinct evolutionary lineages with a complete body cavity: the protostomes and deuterostomes.  These two groups are distinguished by which of the two openings develops into the adult’s mouth.  In the protostomes (insects, worms, snails), during development the opening which will become the mouth forms first.  In the deuterostomes (echinoderms and vertebrates – including humans) the opening that becomes the adult anus forms first during the organism’s development. This distinction is important to understand as we learn more about organismal growth and development in subsequent chapters.

For more information on this concept, be sure to focus on:

  • In Section 3.6, Animals evolved complete body cavities

Tying it all together

Several concepts presented in this chapter build upon concepts presented in previous chapters and are also revisited and discussed in greater detail in subsequent chapters, including:

Eukaryotic Cell Structure

  • Chapter 5 – Section 5.4, The Specialized Internal Compartments of Eukaryotic Cells


  • Chapter 8 – Section 8.2, Photosynthesis: Capturing Energy from Sunlight


  • Chapter 8 – in Section 8.2, Chloroplasts are the sites of photosynthesis

Sexual Reproduction and Animal Development

  • Chapter 29, Reproduction and Development

Animal Behavior

  • Chapter 30, Behavior

Plant Pollination

  • Chapter 32 - Section 32.3, Producing the Next Generation: Flower Form and Function


  • Chapter 33, The Biosphere

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