BIMM 120 Midterm questions and
correct answers graded A+
Evolution - correct answer ✔✔ -accounts for similarities between organisms and diversity of life
-based on genetics and ecology
-evolution from changes in genetic info carried by DNA
-DNA can change by mutations
-DNA exchange by sexual reproduction or horizontal gene transfer greatly enhances genetic
variability.
-Organisms compete for resources in their environment and some individuals are better at
survival, reproduction, and passing on their genes
Gene Similarity - correct answer ✔✔ • Similarities in DNA, RNA, ribosomes, proteins, etc.
demonstrate a last universal common ancestor (LUCA) for all life (on Earth).
• Organisms that are more similar have more similar genes and DNA sequence, and share a
more recent common ancestor.
• DNA sequence analysis demonstrate evolutionary relationships.
phylogentic Tree - correct answer ✔✔ bacteria, archaea, eukarya
The Origin of Species by Charles Darwin - correct answer ✔✔ • Charles Darwin provided the
core theme of biology in 1859 when he presented two main concepts in The Origin of Species.
1. Contemporary species arose from a succession of ancestors through "descent with
modification" (genetics and evolution).
2. The mechanism of evolution is natural selection (ecology).
,Natural Selection - correct answer ✔✔ • Darwin synthesized the idea of natural selection from
two observations.
1. Individuals in a population of any species vary in many heritable traits. (Genetics). (Bacteria
are present in huge numbers, which produces genetic variability.)
2. Any population can potentially produce far more offspring than the environment can support.
(Ecology)
• This creates a struggle for existence among genetically variant members of a population.
• Individuals with traits best suited to the local environment will generally leave more surviving,
fertile offspring.
• Natural selection is differential reproductive success.
• Populations of organisms evolve as better-adapted individuals outcompete others. (Antibiotic
resistant bacteria)
Mutant - correct answer ✔✔ • Mutations are changes in genetic information
- DNA sequence changes
- Gain and loss of genes
• A common misunderstanding is that mutations are bad and mutants are weird and defective,
but this is not correct.
- Mutations can be good, bad, or irrelevant.
• Except for identical clones, each individual organism has different genetic information and
could be considered a mutant.
• Someone with cystic fibrosis is a mutant, but Albert Einstein and Michael Jordon are mutants
too
Evolution Future
Didn't fish evolve legs to live on land? Didn't apes evolve into humans? - correct answer ✔✔ •
Evolution has no future goals or direction. Populations evolve, not individual organisms.
• Fish that can get more food or escape a predator by occasionally crawling out of the water
might be more successful. A new population is eventually created.
,• Modern fish and land-dwelling vertebrates have a primitive common ancestor in their genetic
history.
• Gorillas and humans have a common ancestor.
- ALL current life on earth has a common ancestor (LUCA).
Species - correct answer ✔✔ • The concept of a species is a human convention used to classify
organisms.
• The difference between species, subspecies, and varieties is made arbitrarily along a
continuum.
• Species boundaries are sometimes vague in populations.
- Organisms are often reclassified as new information becomes available; this is especially true
for bacteria
- For example, are populations that can breed in the laboratory but that never breed in nature
the same or different species?
• The concept of a species is particularly problematic for bacteria because they do not
reproduce sexually.
- The definition of bacterial species is vague and arbitrary
- A current common definition is a whole-genome similarity with an average nucleotide identity
of orthologous genes of 95%.
Humans always evolving-not perfect - correct answer ✔✔ Populations evolve to be "better"
suited to their environment, but there is no evolutionary pressure to become perfect
• Evolution is simply a consequence of genetics and natural selection that results in "good
enough".
- Evolution works on existing genetic variability in populations. It does not produce genetic
changes and it cannot have future goals.
• Evolution has produced some pretty weird characteristics and organisms.
- For example, many sexual characteristics that enhance mating but not adaption to the
environment
, Why hasn't an organism evolved that can outcompete all other organism? - correct answer ✔✔
• Because other organisms, including competitors, predators, pathogens, and parasites are
evolving too. Environments are complex and changing.
• Competition between organisms is fierce in most environments.
• However, there are a few extreme environments where one or only a few organisms are
dominant. For example, salt evaporation ponds are dominated by certain photosynthetic
halophilic Archaea microorganisms because very few organisms can survive in saturated
saltwater
Microorganisms (Microbes) - correct answer ✔✔ § Microorganisms (Microbes) grow almost
everywhere.
- A human body contains far more microbial cells than it does human cells.
- on skin, in gut...
§ Microbes were the first life on Earth.
§ For the first two billion years, all life was microbial.
§ A microbe is a living cellular organism that requires a microscope to be seen (usually).
- Microbial cells range in size from millimeters (mm) down to 0.2 micrometer (µm)
- average is 1-2 µm (How big is that?)
- Viruses may be ten times smaller
- But they are not cells
§ Most microbes consist of single cells.
§ But some microbes are multicellular (examples? fungi, algae)
Exceptions to Microbe definition - correct answer ✔✔ § The simple definition of a microbe
leaves us with some exceptions to the rule.
̵ 1. Supersize microbial cells, 1 mm diameter
- Example: Thiomargarita namibiensis
correct answers graded A+
Evolution - correct answer ✔✔ -accounts for similarities between organisms and diversity of life
-based on genetics and ecology
-evolution from changes in genetic info carried by DNA
-DNA can change by mutations
-DNA exchange by sexual reproduction or horizontal gene transfer greatly enhances genetic
variability.
-Organisms compete for resources in their environment and some individuals are better at
survival, reproduction, and passing on their genes
Gene Similarity - correct answer ✔✔ • Similarities in DNA, RNA, ribosomes, proteins, etc.
demonstrate a last universal common ancestor (LUCA) for all life (on Earth).
• Organisms that are more similar have more similar genes and DNA sequence, and share a
more recent common ancestor.
• DNA sequence analysis demonstrate evolutionary relationships.
phylogentic Tree - correct answer ✔✔ bacteria, archaea, eukarya
The Origin of Species by Charles Darwin - correct answer ✔✔ • Charles Darwin provided the
core theme of biology in 1859 when he presented two main concepts in The Origin of Species.
1. Contemporary species arose from a succession of ancestors through "descent with
modification" (genetics and evolution).
2. The mechanism of evolution is natural selection (ecology).
,Natural Selection - correct answer ✔✔ • Darwin synthesized the idea of natural selection from
two observations.
1. Individuals in a population of any species vary in many heritable traits. (Genetics). (Bacteria
are present in huge numbers, which produces genetic variability.)
2. Any population can potentially produce far more offspring than the environment can support.
(Ecology)
• This creates a struggle for existence among genetically variant members of a population.
• Individuals with traits best suited to the local environment will generally leave more surviving,
fertile offspring.
• Natural selection is differential reproductive success.
• Populations of organisms evolve as better-adapted individuals outcompete others. (Antibiotic
resistant bacteria)
Mutant - correct answer ✔✔ • Mutations are changes in genetic information
- DNA sequence changes
- Gain and loss of genes
• A common misunderstanding is that mutations are bad and mutants are weird and defective,
but this is not correct.
- Mutations can be good, bad, or irrelevant.
• Except for identical clones, each individual organism has different genetic information and
could be considered a mutant.
• Someone with cystic fibrosis is a mutant, but Albert Einstein and Michael Jordon are mutants
too
Evolution Future
Didn't fish evolve legs to live on land? Didn't apes evolve into humans? - correct answer ✔✔ •
Evolution has no future goals or direction. Populations evolve, not individual organisms.
• Fish that can get more food or escape a predator by occasionally crawling out of the water
might be more successful. A new population is eventually created.
,• Modern fish and land-dwelling vertebrates have a primitive common ancestor in their genetic
history.
• Gorillas and humans have a common ancestor.
- ALL current life on earth has a common ancestor (LUCA).
Species - correct answer ✔✔ • The concept of a species is a human convention used to classify
organisms.
• The difference between species, subspecies, and varieties is made arbitrarily along a
continuum.
• Species boundaries are sometimes vague in populations.
- Organisms are often reclassified as new information becomes available; this is especially true
for bacteria
- For example, are populations that can breed in the laboratory but that never breed in nature
the same or different species?
• The concept of a species is particularly problematic for bacteria because they do not
reproduce sexually.
- The definition of bacterial species is vague and arbitrary
- A current common definition is a whole-genome similarity with an average nucleotide identity
of orthologous genes of 95%.
Humans always evolving-not perfect - correct answer ✔✔ Populations evolve to be "better"
suited to their environment, but there is no evolutionary pressure to become perfect
• Evolution is simply a consequence of genetics and natural selection that results in "good
enough".
- Evolution works on existing genetic variability in populations. It does not produce genetic
changes and it cannot have future goals.
• Evolution has produced some pretty weird characteristics and organisms.
- For example, many sexual characteristics that enhance mating but not adaption to the
environment
, Why hasn't an organism evolved that can outcompete all other organism? - correct answer ✔✔
• Because other organisms, including competitors, predators, pathogens, and parasites are
evolving too. Environments are complex and changing.
• Competition between organisms is fierce in most environments.
• However, there are a few extreme environments where one or only a few organisms are
dominant. For example, salt evaporation ponds are dominated by certain photosynthetic
halophilic Archaea microorganisms because very few organisms can survive in saturated
saltwater
Microorganisms (Microbes) - correct answer ✔✔ § Microorganisms (Microbes) grow almost
everywhere.
- A human body contains far more microbial cells than it does human cells.
- on skin, in gut...
§ Microbes were the first life on Earth.
§ For the first two billion years, all life was microbial.
§ A microbe is a living cellular organism that requires a microscope to be seen (usually).
- Microbial cells range in size from millimeters (mm) down to 0.2 micrometer (µm)
- average is 1-2 µm (How big is that?)
- Viruses may be ten times smaller
- But they are not cells
§ Most microbes consist of single cells.
§ But some microbes are multicellular (examples? fungi, algae)
Exceptions to Microbe definition - correct answer ✔✔ § The simple definition of a microbe
leaves us with some exceptions to the rule.
̵ 1. Supersize microbial cells, 1 mm diameter
- Example: Thiomargarita namibiensis
