BIO104 Exam 1

What is biodiversity? 

It includes: 

• Species diversity (different species) 

• Genetic diversity (differences within a species) 

• Ecosystem diversity (different habitats and ecosystems) 

Why does biodiversity matter and how do we know? 

• Makes ecosystems more stable and resilient 

• Increases productivity (more plant growth) 

• Provides ecosystem services like food, clean water, pollination, and disease control 

• Helps ecosystems recover from disturbances (fires, droughts, pests) Experiments show ecosystems with more species perform better (higher productivity) 

• Long-term studies show diverse ecosystems recover faster after disturbances 

• Comparisons show biodiversity loss leads to ecosystem collapse, dead zones, or reduced yields 

principles and components of the scientific process 

logical way to answer questions using evidence. 

Main components: 

1. Observation 

2. Question 

3. Hypothesis (testable explanation) 

4. Prediction 

5. Experiment or data collection 

6. Analysis 

7. Conclusion 

8. Communication 

Key principles: 

• Based on evidence 

• Testable and repeatable 

• Open to revision 

• Conducted within a scientific community 

Formulate a testable hypothesis and design a controlled experiment 

changes one thing at a time. 

Example: 

• One group gets fertilizer 

• One group does not 

• Everything else stays the same 

• Variables & groups 

  • Independent variable: what you change 

  • Dependent variable: what you measure 

  • Control group: no treatment 

  • Experimental group: gets the treatment 

  Interpreting data 

  • Look for patterns 

  • Compare groups 

  • Decide if results support the hypothesis 

Identify the independent and dependent variables and control/experimental groups 

 what you change,  what you measure, the cause and the effect

What are control and experimental groups?

does not get the treatment, gets the treatment 

different kinds of data 

• Quantitative data: numbers (height, mass, temperature) 

• Qualitative data: descriptions (color, behavior, presence/absence)  1.Compare control vs experimental 

2. Look for patterns or differences 

3. Decide if results support the hypothesis 

Describe the different ways biological diversity can be measured and how estimates of diversity are calculated. 

1. Species richness 

• Number of different species in an area 

• Example: 10 species vs. 3 species 

2. Species evenness 

• How evenly individuals are spread among species 

• High evenness = similar numbers of each species 

• Low evenness = one species dominates 

3. Diversity indices 

• Combine richness + evenness into one number 

• Common examples: Shannon index  

• Higher value = higher diversity 

 Describe methods of sampling used to estimate diversity. 

Scientists estimate biodiversity by sampling using quadrats, transects, random or stratified sampling, and mark–recapture methods depending on the habitat and organisms. 

Scientists sample an area (quadrats, transects) 

• Count species and individuals 

• Use equations to estimate total diversity 

• Rarefaction curves show how diversity changes with sampling effort 

Practice calculating Shannon Index (H’) 

• Higher H’ = higher biodiversity 

• Accounts for richness + evenness 

 

• Explain why a rarefaction plot is made, what data are used, and how these plots are interpreted. 

Formula 

H′=−∑(piln⁡pi)H' = -\sum (p_i \ln p_i)H′=−∑(pi lnpi )  

• pi  = proportion of individuals in species  

• ln⁡\ln = natural log 

Explain why a rarefaction plot is made, what data are used, and how these plots are interpreted. 

To compare biodiversity fairly when sample sizes differ 

What data are used? 

• Number of individuals sampled 

• Number of species observed 

Axes 

• X-axis: number of individuals (or samples) 

• Y-axis: species richness 

How to interpret 

• Steeper curve → many new species found quickly 

• Curve leveling off → most species have been sampled 

• Higher curve = higher species richness 

Use biodiversity estimates to inform decisions 

help scientists and managers: 

• Decide which areas to protect 

• Compare habitat quality 

• Detect environmental damage 

• Track restoration success 

Example decisions 

• Protect areas with high H’ 

• Increase sampling if rarefaction curve hasn’t leveled off 

• Restore habitats with low diversity 

How does the tilt and shape of the Earth create both the seasons and atmospheric circulation patterns? 

• The Earth is round, so sunlight hits it unevenly 

• The equator gets more direct sunlight 

• The poles get less direct sunlight 

• The Earth is tilted as it orbits the Sun 

• Different parts of Earth receive more or less sunlight during the year 

• When the Northern Hemisphere is tilted toward the Sun → summer 

• When it is tilted away from the Sun → winter 

• Seasons are caused by tilt, not distance from the Sun 

• Warm air at the equator rises 

• Cool air near the poles sinks 

• Air moves from high pressure to low pressure 

• Earth’s rotation (Coriolis effect) causes air to curve 

• This creates global wind patterns (Hadley, Ferrel, Polar cells

 How does energy move in an ecosystem? 

Energy enters ecosystems as sunlight 

1. Producers (plants, algae) capture sunlight by photosynthesis 

2. Energy moves to consumers when organisms eat plants or other animals 

3. Decomposers break down dead matter and use remaining energy 

• Energy flows in one direction 

• Energy is lost as heat at each step 

• Only a small fraction (~10%) moves to the next level 

Use global, seasonal, or diurnal patterns of CO2 emissions to infer the relative magnitudes of gross primary production and respiration. 

CO₂ taken out of the air by photosynthesis 
CO₂ put into the air by plants, animals, and microbes 

• Daytime: CO₂ usually decreases → photosynthesis (GPP) > respiration 

• Night: CO₂ increases → only respiration is happening 

• Spring & summer (especially in Northern Hemisphere): CO₂ goes down → lots of plant growth, GPP > respiration 

• Fall & winter: CO₂ goes up → less photosynthesis, respiration > GPP 

• CO₂ is lowest after peak growing season and highest after winter → shows that plant photosynthesis strongly affects atmospheric CO₂, but respiration still adds CO₂ year-round 

difference between climate and weather. 

• Short-term conditions 

• What’s happening today or this week 

• Example: “It’s raining and 45°F in North Carolina today” 

• Long-term average patterns (years to decades) 

• What you expect over time 

• Example: “North Carolina usually has mild winters and hot, humid summers” 

 

Why does nutrient cycling matter for biodiversity? 

All living things need nutrients (like nitrogen and phosphorus) to grow and survive. 

• keeps those nutrients moving through soil, water, plants, animals, and microbes. 

• When nutrients are available and recycled, more species can survive → higher biodiversity. 

• If nutrients are lost or limited, fewer species can live there → lower biodiversity. 

Use a simple compartment model of nutrient cycling to account for all inputs and outputs for an ecosystem. 

• Soil 

• Plants 

• Animals 

• Decomposers (microbes) 

Sunlight (energy, not recycled) 

Nutrients from: 

• Weathering of rocks 

• Atmospheric deposition (rain, nitrogen fixation) 

• Soil → Plants (nutrient uptake) 

• Plants → Animals (eating) 

• Plants & Animals → Decomposers (death, waste) 

• Decomposers → Soil (mineralization) 

Nutrient loss by: 

• Leaching into water 

• Runoff 

• Gas loss to the atmosphere (e.g., denitrification) 

What are the components of the nitrogen cycle? Include the different forms of organic and inorganic nitrogen

• N₂ (nitrogen gas) – in the atmosphere 

• NH₄⁺ (ammonium) – in soil and water 

• NO₂⁻ (nitrite) – in soil (short-lived) 

• NO₃⁻ (nitrate) – in soil and water 

• Amino acids 

• Proteins 

• DNA and RNA 

• Found in plants, animals, microbes, and detritus 

the processes that convert nitrogen from one form to another. 

1. Nitrogen fixation 

• N₂ → NH₄⁺ 

• Done by bacteria (in soil, water, or plant roots) and lightning 

2. Assimilation 

• NH₄⁺ or NO₃⁻ → organic nitrogen 

• Plants take up inorganic nitrogen and build it into tissues 

3. Consumption 

• Nitrogen moves plants → animals through eating 

4. Excretion & death 

• Organic nitrogen returns to soil as waste or dead material 

5. Mineralization (decomposition) 

• Organic nitrogen → NH₄⁺ 

• Done by decomposer microbes 

6. Nitrification 

• NH₄⁺ → NO₂⁻ → NO₃⁻ 

• Done by soil bacteria 

7. Denitrification 

• NO₃⁻ → N₂ (gas) 

• Returns nitrogen to the atmosphere 

Predict changes in pools or fluxes within a compartment model of nutrient cycling based on provided information. 

where nutrients are stored 

• Soil nutrients 

• Plant biomass 

• Animal biomass 

• Detritus / decomposers 

movement between pools 

• Uptake, consumption, decomposition, leaching, gas loss 

If a flux increases, the receiving pool gets bigger, If a flux decreases, the receiving pool gets smaller 

True or false

true

examples of flux and pool changes

• More fertilizer added → soil nutrient pool increases → plant uptake increases 

• More plant growth → plant biomass pool increases → more nutrients for herbivores 

• Deforestation → plant pool decreases → nutrient loss from soil increases (leaching) 

• More decomposition → soil ammonium increases 

Explain how the addition of nutrients affects the biodiversity of an ecosystem; and consider ways to prevent human-caused nutrient inputs. (short term)

• More nutrients → faster plant growth 

• Productivity increases 

• Some species benefit 

Explain how the addition of nutrients affects the biodiversity of an ecosystem; and consider ways to prevent human-caused nutrient inputs. (long term)

• Fast-growing species outcompete others 

• Community becomes less diverse 

• Can cause algal blooms and dead zones in water 

Preventing human-caused nutrient inputs 

• Fertilizers 

• Animal waste 

• Sewage and wastewater 

• Urban runoff 

• Use less fertilizer and apply it carefully 

• Plant buffer strips near rivers and lakes 

• Improve wastewater treatment 

• Use cover crops to absorb excess nutrients 

• Protect wetlands (they filter nutrients)