Download Chapter 1 The Framework of Biology

Chapter 15 Varieties of Life: Prokaryotes, Single-Celled
Eukaryotes, and Algae
CHAPTER OUTLINE
15.1 Understanding biodiversity is an ongoing scientific endeavor.
Scientists have identified many species but with new technologies, many more may be
discovered. Use of DNA analysis, biochemical analysis and electron microscope studies
may reveal more species and provide characteristics which will clarify relationships
within the prokaryotes, single-celled eukaryotes and algae.
15.2 Biological diversity reflects the varied adaptations that species have evolved to
meet common challenges.
Organisms are diverse because they have adapted to various habitats, developing life
histories which allow them to exploit all environments. Although diverse, all life forms
must perform the same basic processes.
15.3 Archaea and Bacteria are distinct domains of prokaryotes.
DNA sequencing has revealed two domains of prokaryotes, Bacteria and Archaea.
Additional characteristics were found through biochemical testing and observation with
electron microscopes. These characteristics show that these organisms arose from a
common ancestor.
Bacteria and archaeans have diverse adaptations.
Prokaryotes inhabit a tremendous diversity of habitats, forming bacterial spores during
times of insufficient water availability. These spores can especially affect human health
in food preparation. Prokaryotes that are 'extremophiles' have adapted to extremely hot,
cold or salty environments.
Archaea and bacteria have diverse ways to obtain and use energy.
Not only are some prokaryotes photosynthetic, obtaining energy from the sun, but there
are also prokaryotes which obtain energy from organic molecules, hydrocarbons and
inorganic compounds. Both aerobic and anaerobic forms persist.
Prokaryotes have diverse cellular structures.
The genetic material of prokaryotes is in the form of a circular DNA along with smaller
pieces called plasmids. Many prokaryotes have flagella which propel them through their
environment. Some prokaryotes have a slimy sheath on the outside of their capsule.
Being small solves many problems.
Gas diffusion and water balance are more easily performed because of prokaryotes' small
size.
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Prokaryotic genetic diversity results from a variety of mechanisms.
Asexual reproduction occurs through binary fission; however, prokaryotes are able to
trade genes during bacterial conjugation as well as pick up free pieces of DNA from the
environment; this is called bacterial transformation.
Some prokaryotes have multicellular life stages.
The multicellular stage of myxobacteria is an important piece of evidence in looking at
how multicellularity may have arisen.
Gram staining helps to identify two different kinds of bacteria.
Bacteria can be divided into two groups by the Gram staining technique, revealing a
characteristic of the cell wall. This identification can be a first step in diagnosing an
illness.
Bacteria have many crucial roles in biological systems.
Bacterial interactions with other organisms include pathogenic interactions as well as
beneficial interactions with forms such as E. coli providing vitamin K in human
intestines.
15.4 Genetic relationships are the basis for grouping single-celled eukaryotes and
algae.
DNA and biochemical analysis have provided a more sound grouping of the diverse
single-celled eukaryotes and algae.
Single-celled eukaryotes live in diverse environments.
Single-celled eukaryotes show many similar adaptations as prokaryotes to diverse and
extreme habitats.
Single-celled eukaryotes have diverse structures.
Along with the typical organelles found in eukaryotic cells, some single-celled
eukaryotes, such as paramecium, have a macronucleus and one or more micronuclei.
Also seen in paramecia are oral grooves, anal pores and contractile vacuoles with radial
canals.
Single-celled eukaryotes have a variety of feeding and reproductive strategies.
There are photosynthetic single-celled eukaryotes as well as those which must ingest food
through filter feeding or engulfing food. Asexual reproduction is common in this group
as is sexual reproduction.
Single-celled eukaryotes can have remarkably complex support and protective structures.
Cytoskeletons and external coverings are two forms of support in single-celled
eukaryotes.
Single-celled eukaryotes play important biological roles.
One ecological role of single-celled eukaryotes is as plankton; many are also pathogenic.
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Algae are diverse groups of photosynthetic organisms.
DNA analysis is critical in algal classification supporting three major groups: green, red
and brown algae. Both single-celled and multicellular forms exist and show some similar
characteristics. Many algae have life cycles called alternation of generations in which a
haploid generation alternates with a diploid generation.
15.5 Prokaryotes, single-celled eukaryotes and algae were among the earliest life
forms.
Fossil evidence of prokaryotes occur as stromatolites. Evolution of prokaryotes, singlecelled eukaryotes and algae are yet under study.
15.6 How do you know? Poisons in the sea.
Algal blooms may result in death of organisms which eat the algae if toxins are present in
the algae. Some of these toxins are neurotoxins.
Now you can understand.
Use of living organisms to clean up pollution is bioremediation. Botulism is caused by a
spore-forming bacterium, Clostridum botulinum. Botox is a form of the botulism toxin
which relaxes facial muscles.
What do you think? How did bacterial flagellum evolve?
A discussion of the evidence found which shows how flagella may have evolved is
presented as support of evolution.
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