General Ecology - Exam 1

A good hypothesis is...

1. predictive
2. restable
3. focused

Standard deviation

the average distance of scores around the mean

Standard error

the name for the standard deviation of a distribution of means

p-value

The probability of the null hypothesis being true (results due to chance) which forms basis for deciding if results are statistically significant. Less than 0.05 is statistically significant, above is not.

R^2

coefficient that measures the proportion of the variation in your dependent variable explained by all of your independent variable (R^2 = 1.0, all points are on regression line)

gross primary productivity

The rate at which producers in an ecosystem capture energy

net primary productivity

The energy captured by producers in an ecosystem minus the energy producers respire

How is primary productivity estimated?

1. measuring standing crop (above ground producer biomass in grams)
2. conducting light/dark experiment (plant in chamber is measured for GPP (light) - respiration (dark) to get NPP)
3. taking satellite photos (photos show area covered by standing crop to estimate large area NPP)

What factors affect net primary productivity in terrestrial ecosystems?

temperature, precipitation, light, nitrogen and phosphorus (both together since both limit the other)

What factors affect net primary productivity in aquatic ecosystems?

light transmission, amount of nutrients (nitrogen and phosphorus)

Liebig's Law of the Minimum

biomass/growth of a species is limited by the scarcest limiting factor

What limits secondary productivity?

1. Rate of primary productivity
2. Efficiencies of energy transfer (assume 10% but can be 5-20%)

consumed energy

the portion of NPP that is consumed by the secondary trophic level

egested energy

the portion of consumed energy that is excreted or regurgitated

assimilated energy

the portion of energy that a consumer digests and absorbs (consumed - egested)

respired energy

the portion of assimilated energy a consumer uses for respiration

Net Secondary Productivity (NSP)

portion of assimilated energy that is passed to the next trophic level (assimilated energy - respired energy)

consumption efficiency

the proportion of the available biomass that is ingested by consumers (consumed energy/net primary productivity)

assimilated efficiency

the proportion of consumed energy that is assimilated (assimilated energy /consumed energy)

net production efficiency

the proportion of assimilated energy that is passed to the next trophic level (net secondary production energy/assimilated energy)

ecological efficiency

the proportion of usable energy transferred from one trophic level to the next (NSP/NPP)

What factors affect consumption efficiency?

hiding from predators, food distribution, palatability

what factors affect assimilated efficiency?

digestion mechanisms, food quality, stoichiometry

What factors affect net production efficiency?

metabolic rate (which is affected by size, exothermic vs endothermic, genome, climate)

ecological stoichiometry

the balance of nutrients in ecological interactions

Why do terrestrial systems have fewer trophic levels than aquatic systems?

Terrestrial producers have more structure and are harder to digest therefore assimilated energy efficiency is lower than in aquatic systems (producers are smaller and easier to digest); more assimilated energy means more energy is available to support more trophic levels

What are nutrient inputs in terrestrial ecosystems?

from weathering --> calcium, phosphorus, magnesium, potassium, iron
from precipitation --> Nitrogen, others in dust

nitrogen fixation

The process of converting atmospheric nitrogen into a form producers can use (biotic: cyanobacteria, plant roots bacteria; abiotic: lightning, combustion, fertilizer production)

nitrogen assimilation

formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment (producers take up either ammonium or nitrate from soil; consumers take up nitrogen by eating producers)

denitrification

process by which bacteria convert nitrates into nitrogen gas

nitrification

bacteria convert ammonium into nitrite and then into nitrate

mineralization

breaking down organic compounds into inorganic compounds; in nitrogen cycle, decomposers break down biological nitrogen compounds into ammonium

what do both a low CN ratio and low Lignin:N ratio indicate?

a faster decomposition rate

decomposition rate

change in mass/change in time

how do we quantify nutrient cycling?

nutrient inputs: weathering, precipitation
nutrient outputs: leaching, volatilization (loss by evaporation)

What did Vitousek and Reiners hypothesize about nutrient retention?

Older growth forests are more efficient with nutrients than new growth forests

What is the thermocline and what ecological concerns does it present?

- thermocline is the thin layer separating the warm water from the cold dense water
- when body of water experiences eutrophication (producers overpopulate), decomposers are overactive and use up all oxygen above thermocline, starving water below thermocline of oxygen from atmosphere

Acid Decomposition (Acid Rain)

Fall of acids and acid forming compounds from the atmosphere to the earth's surface

why is acid decomposition (rain) toxic to plants?

1. important nutrients are leached from soil (including toxic aluminum)
2. plants can't get enough magnesium for proper photosynthesis

photic zone

aquatic zone that light can penetrate (0 - 200m below surface)

aphotic zone

aquatic zone that light cannot penetrate (200m+)

euphotic zone

all wavelengths of light transmitted through water

disphotic zone

some wavelength transmitted through water but not all

What are the ecological consequences of light transmission varying as water gets deeper?

Different producers grow in different zones depending on how much light they need and what wavelengths they absorb (ex. green algae absorbs violet, blue and red light while red algae only absorb blue light)

osmosis

Diffusion of free water through a selectively permeable membrane

How do freshwater organisms osmoregulate?

hyperosmotic to environment; produce large amounts of diluting urine to expel excess water, gills take in solutes from water, kidneys remove ions from urine

How do saltwater organisms osmoregulate?

hypoosmotic to environment; drink large amounts of sea water, release small amounts of urine, solutes are excreted through kidneys and/or gills

How to plants (ex. mangroves) osmoregulate when growing in saltwater?

retaining high amounts of organic solutes so water will diffuse in, salt glands in leaves that secrete salt by active transport

What are the challenges of gas exchange in aquatic ecosystems?

1. getting enough carbon dioxide for photosynthesis
2. getting enough oxygen for respiration
(both have low solubility in water)

What are the physiological adaptations to gas exchange challenges?

1. direct uptake and carboxylation by Rubisco, then conversion to carbon dioxide by secretion of enzymes or hydrogen ion
2. countercurrent flow of blood and oxygen in gills to get more oxygen from environment, low rates of activity, increase hemoglobin amounts

How do fish adapt to very cold waters?

they produce glycerol to act as a "natural antifreeze" to prevent internal fluids form freezing

What has caused the coral reef decline?

1. acidification (carbon dioxide from atmosphere pushes gas exchange equation left, raising water temp)
2. coral bleaching (coral stressed from high water temps expel algae living in tissue)

What is water potential?

the force by which water is moved (positive is pushing, negative is sucking)

What is matric potential?

amount of water bound to the soil matrix (always negative or zero)

What is field capacity?

amount of soil moisture of water content held in soil after excess water has been drained away

what is wilting point?

minimum amount of water in the soil that is required for plants not to wilt

What are some plant structural adaptations against heat and drought?

hairs (increase boundary layer and prevent water loss), light colored hairs (reflect light preventing water loss), thickened cuticle (allows wind to cool off leaves)

What is photorespiration?

a process in plants that releases carbon dioxide, consumes oxygen, and produces no energy or food and occurs as a result of plants closing stomata on warm dry days

What is one adaptation difference between C3 and C4 plants?

C3 plants waste more energy during dry periods on photorespiration than C4 plants. Therefore, C4 plants are more efficient with energy in hot dry climates than C3 plants are.

How do terrestrial animals maintain a healthy salt balance?

salt tubes to expel salt without wasting water in urine, salt glands

What are the costs and benefits of nitrogenous waste products in animals?

1. Ammonia (ex. dolphins) - no additional energy to convert to Urea but very toxic
2. Urea (ex. humans) - more energy required but less toxic in body, sharks and rays use to increase osmotic potential of blood
3. Uric acid (ex. birds) - conserves more water but requires high energy cost

What are the four processes of heat?

1. radiation 2. conduction 3. convection 4. evaporation

What is an animal adaptation for varying temperatures?

ectothermic (maintain internal temperature via metabolism) vs endothermic (rely on environment to heat internal temperature)