Biology Exam 1

What is the difference between a hypothesis and a prediction

A hypothesis is a possible explanation for an observation, while a prediction is the expected result if the hypothesis is correct.

Hypothesis = explains WHY something happens

Prediction = states WHAT you expect to happen if that explanation is correct

What is deductive reasoning in the scientific method?

Using a hypothesis to predict what should happen if the hypothesis is true.

What is the difference between an independent and dependent variable?

Independent: the variable you change

Dependent: the variable you measure

What is the purpose of a control group?

To provide a baseline for comparison and show what happens without the experimental treatment.

What is a confounding variable?

Another variable that differs between groups and could affect the outcome, making it unclear what caused the result.

What should be kept the same between experimental groups?

Everything except the independent variable.

Why is replication important in an experiment?

It increases confidence that the result is due to the treatment rather than something unusual about one experimental unit.

Why is a larger sample size useful?

It reduces the effect of unusual individuals and gives a more reliable estimate of the population.

What is the difference between a control condition and a controlled variable?

A control condition is the baseline used for comparison; a controlled variable is a factor kept the same between groups.

What is an experimental unit?

“What receives the treatment independently?”

What is energy?

The ability to do work

What is biological work?

Any process that requires energy to cause change or maintain living conditions.

Ex: building molecules, moving substances, growth, repair, and movement

Why do living organisms require energy?

Living organisms require energy to perform work, maintain internal order, and grow.

What is the difference between exergonic and endergonic processes?

Exergonic- releases free energy

Endergonic- requires the net input of free energy

What is energy coupling?

An exergonic reaction drives an endergonic process.

What exergonic reaction is commonly coupled to endergonic cellular processes?

ATP hydrolysis: ATP → ADP + Pi.

This reaction is exergonic, so it releases free energy that can be coupled directly to endergonic cellular processes.

What is the role of cellular respiration?

To transfer energy from glucose into ATP, which cells then use to perform work.

What is chemical potential energy?

Energy stored because of a molecule’s structure and chemical bonds.

What are the five properties of life?

Grow & reproduce

React to the environment

Maintain homeostasis

Evolve

Use energy to do work

Which property of life is the exception to requiring energy input, and why?

Evolution; it is a population-level change across generations, not individual cellular work.

Why do the properties of life (except evolution) require energy?

They require biological work to maintain order, grow/reproduce, respond, and maintain homeostasis.

What is the First Law of Thermodynamics?

Energy cannot be created or destroyed; it can only be transferred or transformed.

What does the Second Law of Thermodynamics tell us?

Energetically favorable (spontaneous) processes increase the total entropy of the universe.

What does the sign of ΔG tell you?

whether a process is energetically favorable/spontaneous

How does the sign of ΔG relate to exergonic vs. endergonic?

ΔG < 0 = exergonic/favorable; ΔG > 0 = endergonic/unfavorable; ΔG = 0 = equilibrium.

What is the Gibbs free-energy equation?

ΔG = ΔH − TΔS

How do you determine whether coupled reactions are favorable?

Add their ΔG values. If total ΔG < 0, the coupled process is favorable.

Why are growth, reproduction, response, and homeostasis endergonic?

They require a net input of free energy to build/maintain organized states and perform biological work.

What do positive/negative ΔH, ΔS, and ΔG mean?

ΔH: − = releases heat; + = absorbs heat

ΔS: + = entropy increases; − = entropy decreases

ΔG: − = exergonic/favorable; + = endergonic/unfavorable

What do ΔG, ΔH, T, and ΔS represent, and what do their signs mean?

ΔG = Gibbs free energy: − exergonic/favorable; + endergonic/unfavorable

ΔH = enthalpy: − releases heat; + absorbs heat

T = temperature: measured in Kelvin

ΔS = entropy: + entropy increases; − entropy decreases

What is the difference between bulk flow and diffusion?

Bulk flow moves substances long distances; diffusion handles short-distance exchange.

How does O₂ travel from the atmosphere to a body cell?

Airways: bulk flow → alveoli to blood: diffusion → blood: bulk flow → blood to cell: diffusion.

Why does countercurrent flow increase O₂ extraction?

Opposite flow maintains an O₂ gradient along the entire exchange surface.

What do the variables in Fick’s Law represent?

: \(D\) = diffusion coefficient/permeability; \(A\) = exchange surface area; \(P_{high}-P_{low}\) = partial-pressure gradient; \(L\) = diffusion distance/thickness.

How does each Fick variable affect diffusion rate?

\(D↑, A↑,\) or gradient \(↑\) → rate ↑. \(L↑\) → rate ↓.

What is tidal flow vs. unidirectional flow?

medium moves in and out the same pathway. Unidirectional = medium continuously moves one direction.

Why does countercurrent flow avoid equilibrium along the exchange surface?

Opposite flow continually maintains an O₂ gradient, so diffusion continues along the whole surface.

How does hemoglobin improve O₂ uptake?

t binds O₂, keeps dissolved blood O₂ low, maintains the gradient, and increases O₂ carrying capacity.

What does the right vs. left side of the heart do?

sends deoxygenated blood to lungs. Left → sends oxygenated blood to body.

How do you distinguish arteries from veins?

Arteries carry blood away from the heart; veins carry blood toward the heart.

What is the basic blood-flow pathway through heart and lungs?

body tissues → systemic veins → vena cava → right atrium → right ventricle → pulmonary artery → lung capillaries → pulmonary vein → left atrium → left ventricle → aorta/systemic arteries → systemic capillaries → body tissues

Which pulmonary vessel is oxygenated vs. deoxygenated?

Pulmonary artery = deoxygenated; pulmonary vein = oxygenated.

What happens between the right ventricle and left atrium?

RV → pulmonary artery → lung capillaries → pulmonary vein → LA.

Where does blood become oxygenated?

In lung capillaries, where O₂ diffuses from alveoli into blood.

Where is blood flow slowest, and why?

Capillaries; huge total cross-sectional area slows flow and allows more time for diffusion.

Where is blood pressure highest and lowest?

Highest in arteries; decreases through capillaries; lowest in veins.

Why is blood slowest in the caplliaries

their cross sectional area is the greatest which slows blood velocity. This is useful because it gives more time o2 and co2 to diffuse across capliiary walls

Why can’t organisms maximize every trait at once?

Energy/resources are limited, so investing more in one trait leaves less for others.

What is the order of the main trophic levels?

Producers → primary consumers → secondary consumers → tertiary consumers.

Why can’t trophic efficiency be 100%?

Energy is used in metabolism and lost as heat/waste, so not all becomes biomass.

Which usually transfers more energy upward as biomass: endotherms or ectotherms?

Ectotherms, because less energy is spent on metabolic heat production.

What is an energy pool vs. an energy flux?

Pool = stored energy; flux = energy moving between parts of the ecosystem.

What do \(r>0\), \(r=0\), and \(r<0\) mean?

\(r>0\) growing; \(r=0\) stable; \(r<0\) declining.

n logistic growth, where are \(r\) and \(\Delta N\) maximized?

Per-capita \(r\) is highest at low \(N\); total growth \(\Delta N\) is highest around \(N=K/2\).

Density-dependent vs. density-independent limiting factors

Density-dependent effects increase with population density (competition, disease, predation). Density-independent effects do not depend on population density (storms, fires, freezes).

What happens if environmental degradation lowers \(K\) below the current population size?

The population is now above carrying capacity, so growth becomes negative and the population declines toward the new \(K\).

r-selected vs. K-selected species

r-selected = many offspring, early reproduction, little parental care, variable/disturbed environments. K-selected = fewer offspring, later reproduction, more parental care, stable/crowded environments near \(K\).

Exponential growth

\(\Delta N/\Delta t=rN\)

Logistic growth

\(\Delta N/\Delta t=Nr_{\max}\left(\frac{K-N}{K}\right)\)

Fundamental niche vs. realized niche

Fundamental = full potential range without competition; realized = actual range used in nature, often narrower because of competition.

Why is \(\Delta N\) highest near \(K/2\), not at very low \(N\)?

Low \(N\): \(r\) is high but few reproduce. Near \(K\): many individuals but \(r\) is low. Near \(K/2\), both are moderately high.