Bio 1500 Final Mizzou

Equilibrium

The state where particles are evenly spread and there's no net movement, though individual particles still move.

Dragonfly

Insects that are strong fliers and skilled hunters, catching prey mid-air as adults and hunting underwater as larvae.

Paleozoic Era

Time period over 250 million years ago when dragonflies first appeared.

Meganeura

An ancient, giant dragonfly-like insect from the Carboniferous period with a wingspan over 2 feet—shows how long dragonflies have existed.

Evolutionary Stability

Dragonflies have changed very little over millions of years because their body plan is highly effective for hunting and flying.

Carboniferous Period

A time about 359-299 million years ago when many animals, like giant dragonflies, were much larger than today.

High Oxygen Levels

The atmosphere had more oxygen during the Carboniferous, which allowed animals to grow much bigger than usual.

Gigantism

The tendency for animals to grow to unusually large sizes, common in the Carboniferous due to high oxygen and fewer predators.

Egg

Dragonfly life begins when eggs are laid in or near water.

Naiad (Larva)

Aquatic stage where dragonfly larvae live in water, hunt prey, and grow—can last months to years.

Molting

Process where the larva sheds its skin multiple times as it grows.

Adult

After final molt, the dragonfly emerges with wings, becomes a flying predator, and lives a few weeks to months.

Oxygen Hypothesis

Higher oxygen levels in the Carboniferous allowed dragonflies to grow larger because their bodies could get ore oxygen without lungs.

Lack of Predators Hypothesis

Fewer flying predators back then may have let dragonflies grow bigger without much threat.

Competition Hypothesis

Larger size may have helped dragonflies outcompete others for food or mates.

EarthViewer

An interactive tool that shows how Earth's atmosphere, climate, and life changed over time.

Supporting Evidence

EarthViewer shows that oxygen levels peaked during the Carboniferous, supporting the Oxygen Hypothesis for large dragonflies.

Temporal Correlation

The timing of large dragonflies matches with high oxygen levels, but they shrink as oxygen drops—this weakens other hypotheses like competition or predator absence.

Team-Working Skills

Most important—medical schools and employers highly value the ability to collaborate and work effectively in groups.

Learning Skills

Very Important—being able to adapt and keep learning shows long-term potential.

Communication Skills

Important—clear, respectful communication is key in healthcare and team settings.

Content Skills

Knowing your subject is essential, but it must be paired with people skills.

Least Important: Solo Performance

Doing everything alone is less valued—success today depends on how well you work with others.

Test Weight

Each test counts for 7.6% of your grade—small on its own, so one bad test won't ruin your grade.

Final Exam Opportunity

Worth 17%, the final can raise your grade more than any single test—good chance to recover.

Lab/Discussion Score

Lab and discussion grades are multiplied together, so doing well in both is key for a strong overall score.

Discussion Attendance

Unexcused absences lower your discussion grade, which then lowers the whole lab/discussion score—showing up matters a lot.

Origin of Earth

4.6 billion years ago—Earth forms from dust and gas around the sun.

First Life (Prokaryotes)

3.8 billion years ago—simple, single-celled organisms appear.

Photosynthesis

2.7 billion years ago—cyanobacteria begin producing oxygen, changing the atmosphere.

Eukaryotes

2 billion years ago—complex cells with organelles evolve.

Multicellular Life

1.5 billion years ago—life evolves from single-celled organisms to multicellular forms.

Cambrian Explosion

541 million years ago—rapid diversification of life forms.

First Dinosaurs

230 million years ago—dinosaurs appear and dominate land ecosystems.

Extinction of Dinosaurs

66 million years ago, an asteroid impact led to the mass extinction of dinosaurs, allowing mammals to thrive.

Carboniferous Period

Occurred about 359-299 million years ago, during the Paleozoic Era—a time when Earth's forests grew massive and oxygen levels peaked.

Big Picture Context

The Carboniferous came after the Cambrian Explosion and before the dinosaurs, marking a time of giant insects, swampy forests, and coal formation.

Snowball Earth

A time when Earth was almost completely covered in ice, around 700 million years ago.

Great Oxygenation Event

Around 2.4 billion years ago, cyanobacteria started releasing oxygen, killing off many anaerobic organisms but allowing aerobic life to evolve.

Cambrian Explosion

541 million years ago, life rapidly diversified—most major animal groups appeared in a short time.

Permian Extinction

About 252 million years ago, the largest mass extinction wiped out ~90% of species—caused by volcanic activity and climate change.

Dinosaur Extinction (K-T Event)

66 million years ago, an asteroid hit Earth, ending the reign of dinosaurs and allowing mammals to rise.

High Oxygen Levels

Oxygen made up about 35% of the atmosphere (compared to 21% today), supporting giant insects and amphibians during the Carboniferous.

Swampy Forests

Dense forests with huge ferns, club mosses, and trees grew in wet, tropical lowlands—now the source of coal—during the Carboniferous.

Warm, Humid Climate

The Carboniferous was generally warm and moist, ideal for plant growth and thick vegetation.

Coal Formation

Dead plant material from the swampy forests was buried and compressed over time, forming coal deposits still used today, during the Carboniferous.

Slow Start, Sudden Bursts

Life began early but evolved slowly at first, with major changes (like multicellularity or animal diversity) happening in sudden bursts.

Punctuated Events

Big evolutionary leaps (like the Cambrian Explosion) and extinctions (like the Permian or dinosaur extinction) happened quickly in geologic terms.

Recent Complexity

Most complex life—plants, animals, and humans—appeared relatively late in Earth's 4.6-billion-year history.

Long Periods of Stability

These are followed by short, dramatic changes that shape life's direction.

Rise of Eukaryotes

Higher oxygen levels supported the development of complex cells (eukaryotes) that use oxygen for energy.

Carboniferous Oxygen Peak

During the Carboniferous, oxygen levels were at their highest, enabling giant insects and intense plant growth.

Post-Peak Decline

After the Carboniferous, oxygen levels dropped, leading to the extinction of many large insects and reshaping ecosystems.

Oxygen and Evolution

Increases in oxygen often led to bursts of biological complexity, while drops sometimes triggered extinctions.

Biogenic Oxygen

All oxygen in Earth's atmosphere comes from living organisms—mainly through photosynthesis.

Photosynthesis

Process used by plants, algae, and cyanobacteria to convert sunlight, water, and CO2 into sugar and oxygen.

Cyanobacteria

First organisms to produce oxygen through photosynthesis, starting the buildup of atmospheric O2 about 2.7 billion years ago.

Biogeology

The study of how living organisms have shaped Earth's physical features over time.

Oxygenation of Atmosphere

Life (especially cyanobacteria) added oxygen to the air, changing Earth's atmosphere and enabling new types of rock to form (like rusted iron layers).

Limestone Formation

Shells and skeletons of marine organisms built up over time, creating limestone rock layers.

Diffusion

The movement of particles from an area of high concentration to an area of low concentration, caused by their random motion.

Random Motion

Particles move in all directions due to kinetic energy, bumping into each other and spreading out over time.

Net Movement

Even though individual particles move randomly, overall they tend to spread from crowded to less crowded areas.

Even Distribution

Over time, many particles spread out evenly across a space due to diffusion.

Concentration Gradient

Particles move down the gradient—from high to low concentration—until balance is reached.

Microscopic to Macroscopic

The random motion of single particles leads to predictable large-scale patterns, like even spreading.

Cumulative Effect

Each particle moves randomly, but together they tend to fill available space, creating smooth diffusion patterns.

Statistical Movement

While one particle's movement is unpredictable, the overall behavior of many particles follows a consistent pattern—moving from high to low concentration.

Diffusion Time

The time it takes for particles to diffuse increases with the square of the distance (not linearly).

Distance-Time Relationship

If the distance doubles, diffusion takes four times longer—this makes diffusion slow over long distances.

Efficient Over Short Distances

Diffusion works well in small cells or thin tissues, but is too slow for moving substances far in large organisms.

Size Limitation

Diffusion is too slow over long distances, so organisms must stay small or very thin if they rely only on it.

Need for Transport Systems

Larger organisms evolved circulatory or respiratory systems to move molecules quickly, since diffusion alone isn't enough.

Surface Area-to-Volume Ratio

Small or flat organisms have a high ratio, allowing efficient diffusion across their bodies.

Hypothesis on Insect Size (Clapham and Karr)

Insects were able to grow very large because oxygen levels were higher in the past and there were fewer predators like birds. Once birds evolved, they likely limited insect size by preying on them.

Figure 1 — Insect Wing Size Over Time

The graph shows average insect wing sizes from 320 to 250 million years ago. Wing size increased when oxygen levels were high. Wing size decreased around 150 million years ago—when birds appeared. This suggests that high oxygen helped insects grow large, but bird evolution led to smaller insect sizes over time due to predation pressure.

Evidence Supporting Clapham and Karr's Conclusions

1. Fossil Data: Large insect wings are found in older rocks from times of high oxygen.

2. Timing: Insect size drops right after birds appear in the fossil record.

3. Pattern: Even when oxygen stayed high later, insects still got smaller, showing oxygen wasn't the only factor—birds were likely a cause.

Wavelengths Absorbed by Chlorophyll

Chlorophyll absorbs blue (around 430 nm) and red (around 660 nm) light best. It reflects green, which is why plants look green.

Light-Dependent Reactions

First stage of photosynthesis that happens in the thylakoid membranes.

Inputs: Light, water (H2O), ADP, NADP+

Outputs: Oxygen (O2), ATP, NADPH

Function: Capture light energy to make ATP and NADPH for the next stage.

Light-Independent Reactions (Calvin Cycle)

Second stage of photosynthesis that happens in the stroma of the chloroplast.

Inputs: CO2, ATP, NADPH

Outputs: Glucose (C6H12O6), ADP, NADP+

Function: Use ATP and NADPH to fix carbon and build sugars.

Why O2 Is a By-Product

During light-dependent reactions, water is split (photolysis) to get electrons for energy. The oxygen from water is released as O2, which isn't needed by the plant in this process.

ATP (Adenosine Triphosphate)

The main energy carrier in cells. It transports energy to where it's needed and is the immediate source for cell activities like movement, transport, and building molecules.

Why ATP is Important

When a cell needs energy, it breaks off one phosphate from ATP, turning it into ADP and releasing energy quickly for immediate use.

ATP-ADP Cycle

A repeating cycle where energy is stored and released in cells by switching between ATP and ADP.

ADP to ATP

Chemical Change: ADP + a phosphate (P) -> ATP

Energy Change: Energy is added (from food or sunlight) to bond the phosphate to ADP.

Result: Energy is stored in ATP.

ATP to ADP

Chemical Change: ATP loses one phosphate -> ADP + P

Energy Change: Energy is released for the cell to use.

Result: Energy powers cell processes like muscle movement or protein building.

ATP vs ADP

ATP = Charged battery (energy stored)

ADP = Used battery (needs recharging)

Great Oxygenation Event (GOE)

A major change about 2.4 billion years ago when oxygen levels in Earth's atmosphere rose sharply due to photosynthetic microbes.

Process Leading to GOE

1. Cyanobacteria (blue-green algae) started doing photosynthesis.

2. They used sunlight to turn CO2 and water into glucose and oxygen (O2).

3. Oxygen built up in the oceans, then leaked into the atmosphere over time.

Earth Before GOE

No oxygen in the air. Sky looked orange or purple (due to different gases). Life was anaerobic (didn't need oxygen). Oceans were filled with dissolved iron.

Earth After GOE

Oxygen appeared in the air. Oceans turned blue as iron reacted and settled out. Many anaerobic organisms died (oxygen was toxic to them). New life evolved to use oxygen (aerobic organisms).

Biological Consequences of the Oxygen Revolution

Mass extinction of anaerobic microbes (oxygen was toxic to them). Rise of aerobic organisms that could use oxygen for more efficient energy. Set the stage for complex life (eukaryotes -> animals, plants, etc.).

Geological Consequences of the Oxygen Revolution

Oxygen reacted with dissolved iron in oceans -> formed banded iron formations (BIFs) in rocks. Oceans changed color as iron was removed. Laid down iron-rich layers we mine today.

Atmospheric Consequences of the Oxygen Revolution

Oxygen built up in the air. Formation of the ozone layer (O3), which blocks harmful UV rays. Atmosphere shifted from methane-rich to oxygen-rich, changing climate and chemistry.

DNA (deoxyribonucleic acid)

The molecule that carries the genetic instructions for life. Made of a long chain of nucleotides (A, T, C, G).

Gene

A section of DNA that has the instructions to make a specific protein. Each gene controls a trait (like eye color).

Allele

A version of a gene. For example, a gene for eye color may have a brown allele and blue allele.

Chromosome

A long strand of DNA tightly coiled up. Humans have 46 chromosomes (23 pairs), and each one contains many genes.

Alleles

Different versions of the same gene. Each allele gives instructions for a slightly different form of a trait.

How Alleles Differ

They have small differences in their DNA sequence. These differences can change the protein made, affecting how a trait appears. Example: One allele for eye color may produce brown pigment, another may produce blue.