SCI 100 Final Exam Nancy

Water biological importance

Water is important because cells are mostly water, need water balance, and use water for chemical reactions.

Water balance

Cells must maintain the right amount of water or they can shrink, swell, or burst.

Prokaryotic cells

Cells with a cell membrane, usually a cell wall, and no membrane-bound organelles.

Eukaryotic cells

Cells with a cell membrane and membrane-bound organelles such as a nucleus, mitochondria, or chloroplasts.

Prokaryotic vs eukaryotic

Both have cell membranes and genetic material; eukaryotes have membrane-bound organelles, prokaryotes do not.

Cell membrane

A protective barrier that controls what enters and leaves the cell.

Phospholipid

A molecule with a hydrophilic phosphate head and hydrophobic lipid tails.

Phospholipid bilayer

Two layers of phospholipids arranged with water-loving heads facing water and water-hating tails facing inward.

Hydrophilic

Water-loving; the phosphate head of a phospholipid is hydrophilic.

Hydrophobic

Water-hating; the lipid tails of a phospholipid are hydrophobic.

Cell membrane molecules

Cell membranes contain phospholipids, proteins, and cholesterol.

Membrane proteins

Proteins in the cell membrane can act as gates, channels, receptors, or transport helpers.

Cholesterol in membranes

Cholesterol helps with membrane structure and chemical signaling.

Fluid Mosaic Model

The model that says the membrane is fluid because molecules move, and mosaic because proteins and other molecules are scattered throughout.

Selective permeability

The cell membrane allows some substances to pass through but blocks others.

Semi-permeable membrane

A membrane that lets some substances through but not others.

Diffusion

Movement of a substance from high concentration to low concentration without energy.

Osmosis

The diffusion of water across a semi-permeable membrane.

Concentration gradient

A difference in concentration between two areas.

Solute

The dissolved substance, such as salt or sugar.

Solvent

The substance doing the dissolving; in cells, water is the main solvent.

Hypertonic

More solute and less water compared to another solution.

Hypotonic

Less solute and more water compared to another solution.

Isotonic

Equal solute concentration compared to another solution.

Water movement in osmosis

Water moves toward the side with more solute and lower water concentration.

Dialysis tubing osmosis

If the bag has more sugar than the beaker, water moves into the bag.

Animal cell in hypertonic solution

Water leaves the cell, so the cell shrivels.

Animal cell in hypotonic solution

Water enters the cell, so the cell swells and may burst.

Animal cell in isotonic solution

Water moves in and out equally, so the cell stays normal.

Plant cell in hypertonic solution

Water leaves the cell, causing the plant cell to shrink and the plant to wilt.

Plant cell in hypotonic solution

Water enters the cell, making it turgid; plant cells prefer this because the cell wall prevents bursting.

Cell wall effect in osmosis

Cells with cell walls do not burst as easily because the wall pushes back against incoming water.

Cholera and osmosis

Cholera toxin causes water to leave the body into the intestines, causing severe diarrhea and dehydration.

Rate of osmosis

The speed at which water moves across a semi-permeable membrane.

Temperature and osmosis

Higher temperature usually increases osmosis rate because molecules move faster.

Solute concentration and osmosis

A bigger difference in solute concentration usually increases the rate of osmosis.

Ecology

The study of how organisms interact with each other and with their nonliving environment.

Biotic factors

The living parts of an ecosystem, such as plants, animals, bacteria, fungi, and algae.

Abiotic factors

The nonliving parts of an ecosystem, such as water, sunlight, temperature, rocks, soil, and nutrients.

Species

A group of organisms that can interbreed and produce viable offspring.

Population

All members of one species living in the same place at the same time.

Community

All populations living in the same place at the same time.

Ecosystem

A community of living organisms plus the nonliving abiotic factors around them.

Ecological hierarchy

Species → population → community → ecosystem.

Food chain

A simple series showing who eats whom.

Food web

A visual map of feeding relationships and energy flow among organisms.

Trophic level

A feeding level in a food chain or food web.

Primary producer

An organism that makes its own food, usually through photosynthesis.

Producer examples

Plants, algae, and cyanobacteria.

Primary consumer

An organism that eats producers.

Primary consumer examples

Deer, grasshoppers, rabbits, and zooplankton.

Secondary consumer

An organism that eats primary consumers.

Secondary consumer examples

Frogs, birds that eat insects, small fish, and rodents.

Decomposer

An organism that breaks down dead organisms and waste.

Decomposer examples

Fungi and bacteria.

Rule of Ten

Only about 10% of energy transfers from one trophic level to the next.

Competition

A -/- interaction where both organisms are harmed because they compete for limited resources.

Predation

A +/- interaction where one organism benefits by eating another organism.

Symbiosis

A close ecological relationship between individuals of two or more different species.

Mutualism

A +/+ relationship where both species benefit.

Mutualism example

Bees get nectar from flowers, and flowers get pollinated.

Parasitism

A +/- relationship where one organism benefits and the host is harmed.

Parasitism example

A tick feeding on a deer or a tapeworm living inside a host.

Commensalism

A +/0 relationship where one species benefits and the other is not really affected.

Keystone species

A species whose role in an ecosystem is much larger than its abundance or biomass.

Keystone species removal

Removing a keystone species can cause dramatic changes in the whole community.

Starfish keystone example

Pisaster starfish eat mussels; when starfish are removed, mussels can take over and species diversity drops.

Wolf keystone example

Wolves control elk or deer populations, which can allow plants and other species to recover.

Invasive species

A nonnative species that spreads and causes harm to an ecosystem.

Invasive species impact

Invasive species can outcompete, eat, or replace native species and reduce biodiversity.

Biodiversity

The variety of life in an ecosystem or on Earth.

Genetic diversity

Variation of inherited traits within a species.

Species diversity

The number and abundance of different species in a community.

Ecological diversity

The variety of niches, trophic levels, species, and ecosystem functions in a community.

Biodiversity and stability

High biodiversity usually makes ecosystems more stable and healthy.

Ecosystem services

Benefits humans get from ecosystems, such as food, medicine, clean water, pollination, and recreation.

Biodiversity hotspot

An area with very high biodiversity and many species found nowhere else.

Why islands are hotspots

Islands are isolated, so unique species evolve there that are found nowhere else.

Extinction concern today

Extinction is natural, but biologists are alarmed because the current rate is much faster than normal.

Biggest threat to biodiversity

Habitat loss due to destruction and fragmentation.

Major threats to biodiversity

Habitat loss, invasive species, overexploitation, food web disruption, pollution, and climate change.

Benefits of biodiversity

Food, medicine, ecological/agricultural services, and aesthetic/recreational value.

Benthic macroinvertebrates

Bottom-dwelling organisms without backbones that are large enough to see.

BMIs as biological indicators

Benthic macroinvertebrates show water quality because different species have different pollution tolerances.

Pollution intolerant organisms

Organisms that need cleaner water to survive.

Pollution tolerant organisms

Organisms that can survive in polluted water.

Dichotomous key

A tool used to identify organisms by answering a series of two-choice questions.

Pollution tolerance index

A calculation that uses the types of organisms found to estimate water quality.

Bioaccumulation

The buildup of a harmful substance inside one organism over time.

Biomagnification

The increase in toxin concentration as it moves up a food chain.

DDT

A pesticide that can bioaccumulate and biomagnify, harming organisms at higher trophic levels.

PCBs

Chemicals that can bioaccumulate and biomagnify in food chains.

Silent Spring

A book by Rachel Carson that warned about pesticide dangers, especially DDT, and helped inspire environmental awareness.

Point source pollution

Pollution from one clear source, such as a pipe or factory discharge.

Non-point source pollution

Pollution from many spread-out sources, usually carried by runoff.

Poisoned Waters main idea

Human pollution can damage waterways, ecosystems, wildlife, and human health.

Weather

Short-term daily atmospheric conditions, such as rain, wind, humidity, and temperature.

Climate

Long-term pattern of atmospheric conditions over at least 30 years.

Climate change today

Current climate change is mainly driven by rising greenhouse gases from human activities.

Greenhouse effect

A natural process where gases in the atmosphere trap heat and warm Earth.