Section 2

Question 1

— is the study of the evolutionary history of organisms.

Answer 1

Phylogeny

Question 2

The relationship
between different species or other groups is represented by branching diagrams called
—s (also known as evolutionary trees).

Answer 2

phylogenetic trees

Question 3

The location of the branch
points represents the relative — of different groups. In the example below,
the branch point for gorillas is lower than that for humans and chimpanzees. That
means that gorillas originated—- than humans and chimpanzees. The positions of
the species on the tree indicate c—. Chimps are closer to humans
than gorillas are, so humans are more closely related to chimps than to gorillas.

Answer 3

time of origin
earlier
closeness of relationship

Question 4

Grouping helps
us to ——it reduces large and complex systems into smaller, less complex
systems. But the problem is that the categories we use are—- and the boundaries
we have stipulated between groups are —.

Answer 4

simplify
arbitrary
artificial

Question 5

Classification works by looking for —- between organisms and putting the most
— things together in the same group. Over the last 250 years the specific
structures we look at to find similarities has changed. At first it was large and mostly
— like flowers in plants, body plans in invertebrates or feathers in birds.
As technology got more sophisticated we moved on to comparisons of –,
embryos, — and chemical composition. —- allowed us to use the
structure of tissues and cells to look for similarity. Today, we are been able to look at
the internal instructions, the DNA, and compare it in different species to see how
closely they are related and to hypothesize about who our common ancestors were.

Answer 5

similarities
similar
external features
internal features
behavior
microscopes

Question 6

— is the process of identifying and classifying species. It is used to group
similar organisms based on shared characteristics, which become more specific as the
groups get smaller. It assumes that similar organisms have properties in common and
that similar organisms are closely related to each other. This way of organizing life is
useful because if we know something about one member of a group, we should be able
to apply that knowledge to other members of the same group.

Answer 6

Taxonomy

Question 7

Levels of Taxonomic Classification
--- Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Rodentia
Family Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 7

Domain

Question 8

Levels of Taxonomic Classification
Domain Eukarya
---- Animalia
Phylum Chordata
Class Mammalia
Order Rodentia
Family Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 8

Kingdom

Question 9

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
--- Chordata
Class Mammalia
Order Rodentia
Family Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 9

Phylum

Question 10

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
Phylum Chordata
--- Mammalia
Order Rodentia
Family Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 10

Class

Question 11

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
--- Rodentia
Family Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 11

Order

Question 12

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Rodentia
--- Sciuridae
Genus Sciurus
Species Sciurus niger

Answer 12

Family

Question 13

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Rodentia
Family Sciuridae
--- Sciurus
Species Sciurus niger

Answer 13

Genus

Question 14

Levels of Taxonomic Classification
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Rodentia
Family Sciuridae
Genus Sciurus
----Sciurus niger

Answer 14

Species

Question 15

Each species has its own —- The name is made of two Latin words.
Using this example, all fox squirrels have the scientific name of Sciurus niger

Answer 15

scientific name

Question 16

Please note that the —

name is capitalized but the second word is not capitalized.

Answer 16

genus

Question 17

Scientific names should be—when hand-written or written in italics when
printed. This tradition allows a person to quickly recognize a scientific name, even if
s/he has never seen it before. This also means that other levels of taxonomic
classification — underlined or italicized.

Answer 17

underlined

are not

Question 18

There are a number of different definitions of — in biology. That is partly due to
the difficulty of finding a definition that works for the huge diversity of life on this planet.
Since the main organisms covered in this course are plants and animals, we are going
to use the — concept that applies to organisms that reproduce
sexually.

Answer 18

species

biological species

Question 19

Carl Woese of the University of Illinois has proposed a classification scheme based on
— (ribosomal RNA). In his scheme, used by most biologists today,
organisms are divided into — Domains. Note that Domain Archaea and Domain
Eukarya are more closely related to each other than to Domain Bacteria.

Answer 19

molecular evidence

three

Question 20

Domain — (eubacteria or “true —-“) contains unicellular organisms that
have a prokaryotic cell. A prokaryotic cell lacks a nucleus. These cells are typically
small with no internal organelles. The DNA is usually arranged in one circular ring.
This includes — and cyanobacteria. Organisms such as E. coli or Salmonella or
Staphylococcus aureus are members of this group.

Answer 20

Bacteria

Question 21

Domain – contains simple life forms called —-. These are
also unicellular prokaryotes. Many of the archaeans have been found in hostile
environments. —- include thermoacidophiles that live in very hot acidic
environments, methanogens that produce methane gas, and halophiles that live in very
salty environments. Recent analysis of the 1,738 genes of a species of this group
showed that about half of its genes were totally unique. (In other words, these genes
have not been found in any other plant, animal, bacterium, protist or fungus).

Answer 21

Archaea

Question 22

Domain — contains complex organisms (the —-) that

have cells with nuclei. These organisms include protists, plants, animals and fungi.

Answer 22

Eukarya

eukaryotes

Question 23

Evolution is studied as both a — and a —. The process of evolution focuses
on all of the mechanisms that affect how living things have changed over time (genetic
variation, natural selection, etc.). The — of evolution and its mechanisms will be
discussed later in this course.
The — of evolution is the history of living things on the earth. Biodiversity (all
organisms alive today or in the past) is the result of more than 3.5 billion years of
evolution on this planet, including extinctions and speciation events.

Answer 23

process
result
process
result

Question 24

The first cells were —. As you can see from this tree, bacteria are more
ancient than archaeans. Within Domain Bacteria, there are many groups. One very
important group in the history of life on Earth is —. These photosynthesizing
bacteria were the first to evolve the ability to generate oxygen as a byproduct. This
totally changed everything! Oxygen accumulated in the oceans and the atmosphere,
making it possible for more complex cells (and eventually multicellular organisms) to
evolve. Why? Because oxygen is required to harvest much more energy from food and
it takes a lot of energy to run larger, more complex cells and organisms.

Answer 24

prokaryotes

cyanobacteria

Question 25

What about Domain Archaea? These prokaryotes are fundamentally different in terms
of genetics and chemistry from bacteria. They are more similar to —. Some
scientists propose that the origin of eukaryotic cells involved an archaean ancestor.

Answer 25

eukaryotes

Question 26

Now, let’s talk about Domain Eukarya. Eukaryotic cells are larger and more complex
than prokaryotic cells. In addition to a —, they contain many other internal
structures (—s), including mitochondria and chloroplasts.

Answer 26

nucleus

organelles

Question 27

The nucleus (and some other organelles) probably evolved from infolding of the plasma
membrane (membrane at the cell’s edge). This divided the interior of the cell into many
separate compartments, allowing each cellular function to proceed more efficiently.
The evolution of mitochondria and chloroplasts is more complicated. ---
burn food to provide energy, using oxygen in the process. ---- do
photosynthesis, using sunlight to turn carbon dioxide and water into food and oxygen.
The evolution of mitochondria and chloroplasts involves endosymbiosis

Answer 27

mitochondria

chloroplasts

Question 28

— involves an intimate relationship between two species (symbiosis =
living together) in which one species lives inside the other species (endo = inside). In
other words, the ancestor of eukaryotic cells had different organisms living inside them
that evolved into organelles as the two species became more interdependent.

Answer 28

Endosymbiosis

Question 29

Now let us look at the possibilities for descendants of the ancestral cells. Some
remained —, which means they required organic food. In other words, they
could not make their own food by photosynthesis and had to eat other organisms. All
living—- eukaryotes, including you, are descendants of these cells.

Answer 29

heterotrophic

Question 30

Some ancestral cells went through a second round of endosymbiosis. An ancestral cell
engulfed a cyanobacterium, which was not digested. Instead, the cyanobacterium lived
inside the cell and produced food and oxygen by photosynthesis. The food and oxygen
were shared with the host cell. Over time, the cyanobacterium and the cell became so
dependent on one another that neither could survive on its own. At this point, the
cyanobacterium had become a different organelle, the chloroplast. This lineage was
—, which means they made their own food instead of eating other organisms.
This cell lineage gave rise directly or indirectly to all photosynthetic eukaryotes,
including plants.

Answer 30

autotrophic

Question 31

There are five main lineages of eukaryotes. Among these are some very familiar
organisms: plants, animals and fungi. The familiar groups are surrounded by other
eukaryotes that are not as familiar. Most of these are tiny aquatic organisms, although
some are very large (such as the giant kelp, a type of seaweed). These eukaryotes that
are not plants, animals or fungi are usually called by the informal name “—”.

Answer 31

protists

Question 32

• • are multicellular eukaryotes that make their own food by photosynthesis
    (autotrophs) . Plants include mosses, ferns, horsetails, conifers, and flowering plants.

Answer 32

plants

Question 33

— are multicellular eukaryotes that are absorptive heterotrophs. That means they
cannot make their own food (heterotrophs) so they have to eat other organisms, dead or
alive. They digest their food by secreting chemicals outside of their bodies onto food
particles. Digestion occurs outside the body, and then the fungus absorbs the digested
particles (absorptive). Fungi include mushrooms, molds and yeasts

Answer 33

Fungi

Question 34

Fungi are multicellular eukaryotes that are —. That means they
cannot make their own food (heterotrophs) so they have to eat other organisms, dead or
alive. They digest their food by secreting chemicals outside of their bodies onto food
particles. Digestion occurs outside the body, and then the fungus absorbs the digested
particles (absorptive). Fungi include mushrooms, molds and yeasts

Answer 34

absorptive heterotrophs

Question 35

— are multicellular eukaryotes that are ingestive heterotrophs. Animals cannot
make their own food, either. They bring food into their bodies (ingestive), secrete
chemicals internally to break down the food substances, and then absorb the particles
into their body fluids. Animals include sponges, worms, crustaceans, insects, fishes,
reptiles, birds, and mammals.

Answer 35

Animals

Question 36

Animals are multicellular eukaryotes that are —. Animals cannot
make their own food, either. They bring food into their bodies (ingestive), secrete
chemicals internally to break down the food substances, and then absorb the particles
into their body fluids. Animals include sponges, worms, crustaceans, insects, fishes,
reptiles, birds, and mammals.

Answer 36

ingestive heterotrophs

Question 37

— (all
organisms alive today or in the past) is the result of more than 3.5 billion years of
evolution on this planet, including extinctions and speciation events.

Answer 37

Biodiversity