Campbell Biology Chapter 1 Review: Introduction: Themes in the Study of Life

1.1 Big themes that connect biology

pp. 2–11

On the AP exam? Yes

This overview previews ideas the exam tests later: feedback (4.4), energy flow (8.2), prokaryotic and eukaryotic cells (2.10) and gene expression (6.3–6.4); you won't be asked to list the book's themes.

In the course: Topic 2.10 Origins of Cell Compartmentalization, Topic 4.4 Feedback, Topic 6.3 Transcription and RNA Processing, Topic 6.4 Translation, Topic 8.2 Energy Flow Through Ecosystems, Topic 8.5 Community Ecology (notes, videos and more questions)

Key points

Life is organized in levels: molecules, organelles, cells, tissues, organs, organ systems and organisms, then populations, communities, ecosystems and the whole biosphere.
A level can do things its parts can't do alone. A ribosome builds proteins, but none of its separate RNA and protein pieces can; abilities like this are called emergent properties, and they depend on how the parts are organized.
Biologists take systems apart to study the pieces (reductionism), and they also build models of how all the pieces work together (systems biology). You need both.
Organisms constantly trade materials with their surroundings and with each other. Energy flows one way, usually arriving as sunlight and leaving as heat, while elements like carbon and nitrogen get recycled. Burning fossil fuels has added CO₂ to the air and warmed Earth by more than 1 °C since the late 1800s.
Structure fits function at every level. Cells are the simplest things that are fully alive: an organelle or a molecule can't carry out all of life's processes by itself. Prokaryotic cells have no nucleus or membrane-bound organelles; eukaryotic cells do.
DNA stores inherited information in the order of its four nucleotides (A, T, C and G). Genes are transcribed into RNA, and mRNA is translated into protein using a code that's nearly the same in every organism. The human genome is about 3 billion base pairs long (you carry one copy from each parent) and has roughly 20,000 protein-coding genes.
Feedback regulates living systems. In negative feedback, the result of a process slows or reverses it, which keeps conditions steady; in positive feedback, the result pushes the process even further.

Key terms (15)

biosphere: Every place on Earth where life is found, together with all the living things there.
ecosystem: All the organisms in an area plus the nonliving things they interact with, like soil, water, air and sunlight.
community: The different species living in one place and interacting with each other, taken together.
population: A group of individuals of the same species that share an area at the same time.
emergent property: A feature that appears only when parts are put together in a certain arrangement. No single part has it by itself.
reductionism: An approach that tries to understand a whole by taking it apart and examining each piece separately.
systems biology: An approach that combines data on many interacting parts, such as all the genes and proteins in a cell, into a model of how the whole network behaves.
producer: An organism that makes its own food, usually by capturing light energy in photosynthesis. Plants and algae are producers.
consumer: An organism that gets its energy by eating other organisms.
prokaryotic cell: A cell with no nucleus and no membrane-bound organelles. Bacteria and archaea are made of prokaryotic cells.
eukaryotic cell: A cell whose DNA sits inside a nucleus and that has other membrane-bound organelles. Plants, animals, fungi and protists have eukaryotic cells.
gene expression: Using the information in a gene to make RNA and, for most genes, a protein.
genome: The complete set of genetic material an organism has.
negative feedback: Control in which the result of a process slows or reverses that process, keeping a condition near its set point.
positive feedback: Control in which the result of a process speeds that process up, so the change keeps growing until something ends it.

Check yourself: 1.1 Big themes that connect biology

4 questions on 1.1 Big themes that connect biology. Pick an answer to see if you got it, and why.

Question 1 of 4

A biologist studying a freshwater pond first counts every snail of one species living there. Next she surveys all the snails, fish, plants and algae in the pond. Finally, she measures how water temperature and dissolved oxygen affect those organisms. Which levels of organization did she study, in order?

Question 2 of 4

An enzyme is heated until it unfolds. Its amino acid sequence is unchanged, but it can no longer speed up its reaction. Which idea does this best illustrate?

Question 3 of 4

Which statement best describes how energy and chemical elements move through an ecosystem?

Question 4 of 4

On a fenced grassland reserve, biologists followed a ground squirrel population for several years and recorded the average number of young raised per female at different population densities (invented data). 10 squirrels per hectare: 4.2 young; 20 per hectare: 3.5; 40 per hectare: 2.4; 80 per hectare: 1.1. Which conclusion do these data best support?

0 of 4 answered

1.2 Evolution: why life is so alike and so varied

pp. 11–18

On the AP exam? Yes

Unit 7 tests this directly: natural selection (7.1–7.2), common ancestry (7.6–7.7), reading trees (7.9) and new species (7.10); the focus is reasoning, not memorizing classification ranks.

In the course: Topic 7.1 Introduction to Natural Selection, Topic 7.2 Natural Selection, Topic 7.6 Evidence of Evolution, Topic 7.7 Common Ancestry, Topic 7.9 Phylogeny, Topic 7.10 Speciation (notes, videos and more questions)

Key points

Evolution is biology's central idea: today's organisms are changed descendants of shared ancestors. Shared ancestry explains what living things have in common, and the changes along each branch explain how they differ.
Every species gets a two-part scientific name: its genus, then a species word. Species are sorted into bigger and bigger groups: genus, family, order, class, phylum, kingdom and, broadest of all, domain. There are three domains: Bacteria and Archaea (both prokaryotes) and Eukarya (every organism whose cells have a nucleus).
Within Eukarya, plants make their own food by photosynthesis, fungi digest food outside their bodies and soak up the nutrients, and animals take food in and digest it inside. Protists aren't one natural group; they're spread across several separate branches.
Life shows deep unity, like DNA, a nearly universal genetic code and similar cell parts, because those features were inherited from common ancestors.
Darwin's idea of natural selection starts from a few observations: individuals vary, much of that variation is inherited, and more offspring are born than can survive. Individuals with traits that suit their environment tend to survive and reproduce more.
Over many generations, natural selection makes helpful inherited traits more common, so populations become adapted to their environments. Individuals don't evolve; populations do. When separated populations adapt to different conditions, one species can split into many.
Relationships are drawn as branching trees, and species that split more recently share a more recent common ancestor. Newer DNA evidence suggests eukaryotes branched off from within the archaea, but the AP course still uses the three domain names.

Key terms (15)

evolution: Change in the inherited traits of a population over generations. Over long stretches of time it has produced all of life's diversity.
taxonomy: The science of identifying, naming and classifying living things.
species: A group of organisms that can breed with each other in nature and have offspring that can also reproduce.
domain: The broadest group used to classify life. There are three: Bacteria, Archaea and Eukarya.
Bacteria: A huge, varied domain of prokaryotes found almost everywhere, including in and on your body.
Archaea: A domain of prokaryotes. Many live in extreme places like hot springs or very salty water, and in some of their molecules they're more like eukaryotes than like bacteria.
Eukarya: The domain made up of every organism whose cells have a nucleus: protists, plants, fungi and animals.
protist: Any eukaryote that isn't a plant, animal or fungus. Most are single-celled, and they don't form one natural group.
natural selection: The process in which inherited traits that help individuals survive and reproduce in their environment become more common over generations, because those individuals leave more offspring.
adaptation: An inherited trait that helps an organism survive and reproduce where it lives.
descent with modification: Darwin's phrase for evolution: species come from ancestral species and change along the way.
heritable trait: A characteristic that parents can pass to their offspring through their genes.
common ancestor: An earlier species that two or more later species are all descended from.
phylogenetic tree: A branching diagram that shows a hypothesis about how groups of organisms are related through common ancestors.
adaptive radiation: The fairly rapid evolution of many species from one ancestor, each suited to a different habitat or way of life.

Check yourself: 1.2 Evolution: why life is so alike and so varied

4 questions on 1.2 Evolution: why life is so alike and so varied. Pick an answer to see if you got it, and why.

Question 1 of 4

Archaea and bacteria are both prokaryotes, yet biologists place them in separate domains. Which kind of evidence most strongly supported this split?

Question 2 of 4

A farmer sprays a field with an insecticide. Most of the aphids die, but a few survive and reproduce. After several years of spraying, most aphids in the field are resistant. Which statement best explains this change?

Question 3 of 4

Shore crabs arrived in a bay where a species of sea snail lives. Crabs crack thin shells more easily than thick ones. Biologists recorded the percent of snails with thick shells: 20% when the crabs arrived, 38% after 5 years, 61% after 10 years and 79% after 15 years. Which additional finding would most strengthen the claim that natural selection caused this change?

Question 4 of 4

A phylogenetic tree shows that the lineages leading to species P and species Q split 2 million years ago, and that the lineage leading to P and Q split from the lineage leading to species R 10 million years ago. Which conclusion does the tree support?

0 of 4 answered

1.3 How scientists test ideas

pp. 18–23

On the AP exam? Yes

This isn't one topic: it's the Questions and Methods practice (variables, controls, hypotheses), which the exam tests in every unit, often with data. It's listed under 7.1 because natural selection is the section's example of a theory.

In the course: Topic 7.1 Introduction to Natural Selection (notes, videos and more questions)

Key points

Science answers questions about the natural world with evidence. There's no single fixed recipe: real research loops back and forth between observing, asking, predicting and testing.
Data can be qualitative (descriptions, sketches) or quantitative (measurements recorded as numbers). Both count as evidence.
Inductive reasoning builds a general rule from many specific observations. Deductive reasoning starts from a general idea and works out what specific results you should see if it's true, often written as "if… then…".
A good hypothesis is testable and falsifiable, meaning some result could show it's wrong. Tests can support a hypothesis or rule it out, but they never prove it with total certainty. Claims about supernatural causes can't be checked by any observation, so science can't address them.
In a controlled experiment, you change one factor (the independent variable) and measure its effect on another (the dependent variable), comparing a treated group with a control group. Some conditions can never be held perfectly steady, but if both groups experience them equally, the difference between the groups still points to the factor you changed.
One surprising result isn't enough; a finding gains weight when independent groups repeat the work and get the same outcome.
In science, a theory isn't a guess. A theory like evolution by natural selection is a well-tested explanation that ties together many kinds of evidence and keeps leading to new questions to test, though it can still be revised if strong new evidence doesn't fit.

Key terms (15)

qualitative data: Observations recorded as descriptions, drawings or photos instead of numbers.
quantitative data: Observations recorded as numbers, such as lengths, counts, masses or temperatures.
inductive reasoning: Reasoning from many specific observations to a general conclusion.
deductive reasoning: Reasoning from a general idea to a specific prediction: if the idea is true, then this result should happen.
hypothesis: A possible explanation for an observation that can be tested with more observations or experiments.
prediction: A specific result you'd expect to see if a hypothesis is correct.
falsifiable: Able to be shown wrong. A falsifiable hypothesis has some possible result that would prove it false.
controlled experiment: An experiment that compares an experimental group with a control group that differs only in the factor being tested.
experimental group: The group in an experiment that gets the treatment or condition you're testing. You compare it with the control group to see what the treatment does.
control group: The group that doesn't get the treatment being tested. It shows what happens without it, so you have something to compare to.
independent variable: The factor a scientist changes on purpose to see what effect it has.
dependent variable: The factor a scientist measures to see how it responds to the independent variable.
controlled variables: Conditions kept the same in every group so they can't explain any differences in the results.
repeatability: Whether other scientists get the same results when they repeat an experiment or observation.
scientific theory: A well-tested explanation for a wide range of observations, supported by many independent lines of evidence and still useful for designing new tests.

Check yourself: 1.3 How scientists test ideas

4 questions on 1.3 How scientists test ideas. Pick an answer to see if you got it, and why.

Question 1 of 4

A student measures the activity of 30 different enzymes taken from human cells at several temperatures. Every one works fastest at about 37 °C. She concludes that human enzymes generally work best near body temperature. What kind of reasoning did she use?

Question 2 of 4

Which statement is a testable and falsifiable hypothesis?

Question 3 of 4

To test whether the color of light affects the rate of photosynthesis, a student places identical spinach leaf disks in baking soda solution under red, green or blue light of equal brightness. She counts how many disks float after 15 minutes, since disks float as oxygen builds up inside them. What is the dependent variable?

Question 4 of 4

A researcher thinks compound X blocks catalase, the enzyme that breaks hydrogen peroxide down into water and oxygen. She adds X to 10 tubes of catalase and hydrogen peroxide and finds that little oxygen is produced. What is the most important thing missing from her experiment?

0 of 4 answered

1.4 Science as a shared, social effort

pp. 23–25

On the AP exam? Background

Not tested on its own, but it explains why repeated results carry weight and why model organisms teach us about humans; DNA technology comes back in Topic 6.8.

In the course: Topic 6.8 Biotechnology (notes, videos and more questions)

Key points

Research is mostly teamwork, and a finding becomes part of science only after it's shared through talks and published papers where others can examine it.
Other labs try to repeat important findings. When they can't, the original claim loses support until someone explains the mismatch, which is why faking or cherry-picking data does so much damage.
Model organisms are species that are cheap to keep, reproduce fast and are easy to work with, such as fruit flies, mice and E. coli. Since every species is related through shared ancestors, a gene or process found in one often works much the same way in others, including us.
A question like "why do some people get much sicker from the same virus?" can be studied at the level of genes, cells, whole bodies or entire populations, and each level adds something the others miss.
Science aims to explain how nature works; technology puts that knowledge to practical use, such as a rapid diagnostic test. New tools also open new questions for science, and research done purely out of curiosity often pays off in ways nobody planned.
New technologies raise questions that evidence alone can't answer, such as whether gene-edited mosquitoes should be released into the wild. Answers to those depend on values, law and economics too.
People from different backgrounds bring different questions and ideas, so a more diverse scientific community makes science stronger.

Key terms (13)

model organism: A species that's easy to grow and study in the lab, used to learn things that often apply to many other species.
Drosophila melanogaster: The common fruit fly, a model organism that breeds quickly and has been key to working out how genes control development.
Escherichia coli (E. coli): A bacterium from the gut that's a common model organism for studying genes and cell processes.
Arabidopsis thaliana: A small plant in the mustard family that's the most common model organism for plant biology.
Caenorhabditis elegans: A tiny roundworm that lives in soil. It's a model organism for studying development and the nervous system.
zebrafish: A small freshwater fish with see-through embryos, which makes it a handy model organism for studying how vertebrates develop.
house mouse (Mus musculus): A mammal used as a model organism, especially for studying human genes and diseases.
technology: Putting scientific knowledge to work to make tools, products or methods for a practical purpose.
basic research: Research done to understand how nature works, without a specific practical use in mind.
applied research: Research aimed at solving a particular practical problem, like treating a disease or growing better crops.
peer review: Other experts checking a study's methods and conclusions before it's published.
bioethics: The study of right and wrong in how biology and medicine are used, such as genetic testing or cloning.
genetic testing: Analyzing a person's DNA to find out whether they carry particular alleles, such as ones linked to a disease.

Check yourself: 1.4 Science as a shared, social effort

4 questions on 1.4 Science as a shared, social effort. Pick an answer to see if you got it, and why.

Question 1 of 4

Researchers take yeast cells that are missing a gene they need in order to divide, and give them the matching gene from humans. The yeast cells start dividing normally again. Which is the best explanation for this result?

Question 2 of 4

A lab reports that a new drug stops human skin cells at the G₁ checkpoint of the cell cycle. Three other labs follow the same methods and find that the drug has no effect on the cell cycle. What is the most appropriate scientific response?

Question 3 of 4

Which of the following is best described as technology rather than basic science?

Question 4 of 4

Scientists can now engineer a "gene drive" that spreads through wild mosquito populations and leaves them unable to carry malaria. Which question depends mainly on values and policy choices rather than on scientific evidence?

0 of 4 answered