Campbell Biology Chapter 40 Review: Basic Principles of Animal Form and Function

40.1 Body plans, tissues and coordination

pp. 852–860

On the AP exam? Background

Tissue types and organ systems aren't tested in the current course. What carries over is surface area-to-volume ratio (Topic 2.2), how hormones and nerve signals reach their targets (Topic 4.1), and convergent evolution as a result of natural selection (Topic 7.2).

In the course: Topic 2.2 Cell Size, Topic 4.1 Cell Communication, Topic 7.2 Natural Selection (notes, videos and more questions)

Key points

Physics limits what bodies can look like. Pushing through water, holding up a heavy frame and trading heat with the surroundings steer unrelated animals toward similar shapes, which is convergent evolution.
Every cell has to trade nutrients, gases and wastes with a watery fluid across its membrane. A tiny or very thin animal can do this right at its outer surface, but a big, compact one can't, because its volume grows faster than its outside surface.
Large animals solve this with exchange surfaces tucked inside the body and folded or branched to pack in a huge area, as in the lungs and the gut lining. Blood and the fluid between cells (interstitial fluid) carry materials between those surfaces and every cell.
Bodies are built in levels: cells form tissues, tissues form organs, and organs that cooperate form organ systems. One organ can serve more than one system.
Animals have four main kinds of tissue. Epithelial tissue forms the body's coverings and linings, connective tissue holds parts together and props them up (scattered cells in plenty of matrix), muscle tissue contracts, and nervous tissue carries information.
Two systems coordinate the body. Hormones ride in the blood and affect any cell with the matching receptor, slowly but for a long time. Nerve signals travel set routes to particular cells, fast and briefly.

Key terms (14)

anatomy: The study of an organism's structure: what its parts are and how they're arranged.
physiology: The study of how an organism's parts work, from single cells up to whole organ systems.
convergent evolution: Unrelated species evolving similar features because they face the same challenge, like the long, sticky tongues of anteaters and pangolins, which both eat ants.
interstitial fluid: The watery fluid filling the spaces between cells. Cells swap nutrients and wastes with it, and it swaps with the blood.
tissue: A group of similar cells that work together on one job.
organ: A body part built from several kinds of tissue working together, like the heart or stomach.
organ system: A set of organs that cooperate on a major body function, such as digestion or gas exchange.
epithelial tissue: Tissue made of cells packed edge to edge into layers. It forms the skin's surface and the inner lining of hollow organs and tubes, acting as a barrier and a gatekeeper.
connective tissue: Tissue that is mostly matrix, the material cells secrete, with cells dotted through it. It holds other tissues together and supports them. Bone, cartilage, blood, fat and tendons are examples.
extracellular matrix: The material cells secrete around themselves, such as collagen fibers, which gives a tissue its strength and shape.
muscle tissue: Tissue made of cells that shorten using actin and myosin. Vertebrates have skeletal, cardiac and smooth types.
nervous tissue: Tissue made of neurons, which carry electrical and chemical signals, plus glial cells that support them.
hormone: A signaling molecule released into the blood that changes the activity of target cells with the matching receptor, often far from where it was made.
endocrine system: The glands and cells that release hormones into the blood. It controls slower, body-wide processes like growth and metabolism.

Check yourself: 40.1 Body plans, tissues and coordination

4 questions on 40.1 Body plans, tissues and coordination. Pick an answer to see if you got it, and why.

Question 1 of 4

Fossil insects from about 300 million years ago include dragonfly relatives with wingspans near 70 cm, far bigger than any insect alive today. Insects get O₂ through air tubes that run inward from the body surface, so O₂ reaches their tissues mainly by diffusion. One hypothesis links these giants to air that was about 30% O₂, compared with 21% today. If the hypothesis is right, why would more O₂ allow bigger insects?

Question 2 of 4

Moles (mammals) and mole crickets (insects) both have broad, shovel-like front limbs that they use to dig through soil. Their most recent common ancestor had no such limbs. What best explains the similarity?

Question 3 of 4

In some inherited disorders, the body makes abnormally weak collagen fibers. Which tissue type would be most directly weakened, and which symptom fits?

Question 4 of 4

In a fish's gills, O₂ must diffuse from the water into the blood within a fraction of a second. Which tissue structure would best suit the surface where this exchange happens?

0 of 4 answered

40.2 Homeostasis and feedback loops

pp. 860–862

On the AP exam? Yes

Topic 4.4 tests negative and positive feedback directly. Circadian rhythms and acclimatization are background, though responses to the environment come up in Topic 8.1.

In the course: Topic 4.4 Feedback, Topic 8.1 Responses to the Environment (notes, videos and more questions)

Key points

For any one variable, an animal is either a regulator, holding its internal level steady, or a conformer, letting it follow the outside. The same animal can regulate one variable and conform for another.
Homeostasis means keeping internal conditions within a narrow band while the world outside changes. In people, body temperature stays near 37 °C and blood pH stays close to 7.4.
A control loop has a set point (the target), a sensor that notices a change, a control center that compares it with the target, and a response that pushes the variable back.
Negative feedback is homeostasis's main tool: the response cancels the change that set it off. Because responses take time, the variable wobbles around the set point instead of staying perfectly flat.
Positive feedback does the opposite: the response makes the change bigger and drives a process to a finish, as in milk release during nursing or blood clotting. It isn't how animals hold things steady.
The target itself can move in a planned way: over a lifetime (for example at puberty), over a monthly hormone cycle, or over each day with the circadian rhythm, an internal clock of about 24 hours that daylight keeps on time.
Acclimatization happens inside one animal, which adjusts to new conditions over days or weeks without any change to its genes. Adaptation happens to a population, whose inherited traits shift by natural selection over many generations.

Key terms (11)

regulator: For a given variable, such as temperature, an animal that holds its internal value steady no matter what its surroundings do.
conformer: For a given variable, an animal whose internal value simply follows whatever the outside value is.
homeostasis: Keeping the body's internal conditions within a narrow range despite changes inside or outside.
set point: The target value a control system aims for, like about 37 °C for human body temperature.
sensor: The part of a control loop that detects a change in a variable. It's also called a receptor.
control center: The part of a control loop that compares the sensor's information with the set point and sends out signals to respond.
negative feedback: A loop in which the response shrinks or cancels the original change, bringing the variable back toward its set point.
positive feedback: A loop in which the response makes the original change even bigger, pushing a process toward completion.
normal range: The band between a highest and a lowest allowed value that a regulated variable can drift within before the body responds.
circadian rhythm: A cycle of changes in the body that repeats about every 24 hours. It's driven by an internal clock and kept in step by light.
acclimatization: Gradual changes in one animal's body that help it cope with new conditions, like heat, over days to weeks.

Check yourself: 40.2 Homeostasis and feedback loops

4 questions on 40.2 Homeostasis and feedback loops. Pick an answer to see if you got it, and why.

Question 1 of 4

Brine shrimp live in salt lakes. Over one summer, a lake's salt concentration doubles and its water warms from 12 °C to 28 °C. The whole time, the solute concentration of the shrimp's body fluids barely changes, but its body temperature always matches the water. Which description is correct?

Question 2 of 4

When blood calcium drops, cells in the parathyroid glands detect the change and release parathyroid hormone (PTH). PTH causes bone to release calcium into the blood. In this loop, what is the stimulus, and what kind of feedback is this?

Question 3 of 4

Which of the following is an example of positive feedback?

Question 4 of 4

A healthy person drinks a sugary beverage at time 0, and blood glucose is measured every 30 minutes. Time (min) | Blood glucose (mg/dL) 0 | 90 30 | 150 60 | 120 90 | 95 120 | 85 150 | 90 Which statement best explains the pattern?

0 of 4 answered

40.3 Keeping body temperature in range

pp. 862–868

On the AP exam? Yes

Topic 8.2 tests the difference between endotherms and ectotherms, and Topic 4.4 uses body temperature as a negative-feedback example. The names of the heat-transfer modes, countercurrent exchange and the word poikilotherm are background.

In the course: Topic 8.2 Energy Flow Through Ecosystems, Topic 4.4 Feedback, Topic 3.2 Environmental Impacts on Enzyme Function, Topic 3.5 Cellular Respiration (notes, videos and more questions)

Key points

Temperature matters because enzymes, membranes and other proteins only work well within a certain range. Cooling slows most reactions, and overheating makes some proteins work poorly or unfold.
Birds and mammals are endotherms: most of their body heat comes from their own metabolism, which is expensive. Most fishes, amphibians, reptiles and invertebrates are ectotherms, warmed mainly by the sun, warm ground or water around them, so they need far less fuel.
How steady body temperature stays is a separate question. An ectotherm living in water that never changes temperature can be very steady, while some small endotherms let their temperature fall a lot at night. That's why 'cold-blooded' is a misleading label.
Heat moves only from a warmer object to a cooler one, through radiation, conduction, convection and evaporation. An animal stays in range when the heat it gains and the heat it loses even out.
To hold heat in, animals use insulation (fur, feathers, fat), vasoconstriction in the skin, and countercurrent exchange, where blood heading out to a limb warms the blood coming back. To lose heat, they use vasodilation, sweating, panting and behavior such as seeking shade.
Endotherms can turn up heat production by shivering, or without shivering: in brown fat, mitochondria let the energy from fuel escape as heat rather than storing it in ATP.
In mammals, a group of neurons in the hypothalamus works like a thermostat and runs a negative-feedback loop. During many infections, this thermostat's target is moved up, and the result is a fever.

Key terms (15)

thermoregulation: Keeping body temperature within a range where the body's cells can work well.
endotherm: An animal that makes most of its own body heat through metabolism, such as a bird or mammal.
ectotherm: An animal that depends mostly on its surroundings, like sun or warm ground, for body heat, such as a frog or snake.
poikilotherm: An animal with a body temperature that swings widely along with its surroundings.
homeotherm: An animal that holds a nearly constant body temperature, whether its heat comes from inside or outside.
radiation: Heat traveling as electromagnetic waves between objects that aren't touching, like sunshine warming your face.
conduction: Heat passing directly between two things that are touching, like your hand on a cold metal railing.
convection: Heat carried toward or away from a surface by moving air or water.
evaporative cooling: Heat lost when water turns to vapor on a surface, as when sweat dries on your skin.
insulation: A layer such as fur, feathers or fat that makes it harder for heat to pass between the body and the outside.
vasodilation: Widening of blood vessels. In the skin, it brings more warm blood near the surface, so more heat escapes.
vasoconstriction: When blood vessels get narrower. In the skin, it keeps warm blood deeper in the body and cuts heat loss.
countercurrent exchange: An arrangement where two fluids run side by side in opposite directions, so heat or a dissolved substance passes from one to the other along the whole length. In a limb, it keeps heat from leaving the core.
nonshivering thermogenesis: Making body heat without muscle movement. In brown fat, mitochondria let the energy from fuel escape as heat rather than capturing it in ATP.
fever: A body temperature above normal caused by the brain's thermostat being set higher, often during an infection.

Check yourself: 40.3 Keeping body temperature in range

4 questions on 40.3 Keeping body temperature in range. Pick an answer to see if you got it, and why.

Question 1 of 4

On a hot afternoon, a dog lies belly-down on a cool tile floor. Which kind of heat transfer is it mainly using to cool off?

Question 2 of 4

A small fish lives only in a cave spring where the water stays at 18 °C all year. Its body temperature is always within 0.5 °C of the water's. Which description fits it best?

Question 3 of 4

After 20 minutes in freezing wind, a hiker's fingers look pale and feel numb, yet her core temperature stays near 37 °C. What is happening?

Question 4 of 4

On very hot days, when the air temperature is above its body temperature, a red kangaroo licks its forearms, where many blood vessels run close to the skin. Why does this help, when widening those vessels alone would not?

0 of 4 answered

40.4 Energy use, body size and torpor

pp. 868–872

On the AP exam? Yes

Topic 8.2 tests the main ideas: endotherms spend more energy than ectotherms, smaller animals use more energy per gram, and leftover energy goes to growth, storage or reproduction. The terms BMR and SMR are background.

In the course: Topic 8.2 Energy Flow Through Ecosystems, Topic 3.5 Cellular Respiration, Topic 2.2 Cell Size, Topic 8.1 Responses to the Environment (notes, videos and more questions)

Key points

Animals get chemical energy from food. Cells turn most of it into ATP for work and for building molecules, and nearly all of that energy eventually leaves the body as heat.
Metabolic rate is how fast an animal spends energy. Researchers can measure it as heat given off, or more often as the O₂ used or CO₂ released by cellular respiration.
Basal metabolic rate (BMR) is the lowest rate for an endotherm: resting, not digesting, calm and kept at a temperature where it needn't make or shed extra heat. Standard metabolic rate (SMR) is the ectotherm version, and the temperature must be stated because the animal's body temperature follows its surroundings.
At the same body size, an endotherm's minimum metabolic rate is many times an ectotherm's. That's why ectotherms can get by on much less food.
Bigger animals use more energy in total but less per gram. Whole-body metabolic rate rises roughly with body mass to the ¾ power, so a small animal needs more food, oxygen and heartbeats for each gram of its body.
An energy budget shows where an animal's energy goes: basic upkeep, activity, temperature control, growth and reproduction. If intake beats these costs, the extra is stored or used to grow; if it falls short, the animal loses mass.
Torpor lets an animal go quiet and drop its metabolism way down to save energy when food is scarce or the weather is extreme. Hibernation is torpor that lasts through winter; estivation is torpor that gets an animal through heat and drought.

Key terms (11)

bioenergetics: How an organism takes in, converts and spends energy, which sets how much food it needs.
metabolic rate: How fast an animal spends energy: the total of all its body's reactions over a set amount of time.
kilocalorie (kcal): A unit of energy equal to 1,000 calories. The 'Calories' on food labels are really kilocalories.
calorimeter: An instrument that measures metabolic rate directly as heat: the animal sits in an insulated box and the heat it releases is recorded.
basal metabolic rate (BMR): The lowest energy use of an endotherm, measured while it rests, calm, with no food being digested and at a temperature where it needn't make or shed extra heat.
standard metabolic rate (SMR): The lowest energy use of an ectotherm, measured while it rests without food, at a temperature the researcher names.
energy budget: A breakdown of how an animal spends its energy on upkeep, activity, temperature control, growth and reproduction.
torpor: A temporary state in which an animal becomes inactive and its metabolism drops sharply, saving energy through cold, heat or food shortages.
daily torpor: Torpor for part of every day. It's mostly seen in small birds and mammals, which burn energy very fast when they're active.
hibernation: Torpor that lasts for weeks or months through winter. The body's temperature target is turned way down, so the animal can survive cold and a lack of food.
estivation: Torpor during hot, dry periods, like a lungfish sealed in a mud burrow until the rains return.

Check yourself: 40.4 Energy use, body size and torpor

4 questions on 40.4 Energy use, body size and torpor. Pick an answer to see if you got it, and why.

Question 1 of 4

Why is a lizard's standard metabolic rate always reported along with a specific temperature?

Question 2 of 4Calculator allowed

In mammals, whole-body metabolic rate scales with body mass raised to about the ¾ power. About how many times greater is a 2-kg rabbit's metabolic rate per kilogram than a 512-kg horse's?

Question 3 of 4

A student wants to compare the metabolic rates of crickets at two temperatures. Which measurement gives the most direct estimate of metabolic rate?

Question 4 of 4

In a year when fish are scarce, a colony of fur seals has lower adult body mass and fewer pups born than usual. Which explanation fits best?

0 of 4 answered