BIOL 3410 Exam 3 Review

Exam 3 covers lectures “Introduction to Ecology” through “Trophic Interactions”.

Introduction to Ecology

• Objectives:

  • Define ecology

  • Understand abundance and distribution and the distinction between habitat and niche.

  • Explain the rules of nature - conservation of energy, conservation of mass, and evolution.

  • Describe hierarchy of ecological organization.

  • Understand that organisms play diverse roles in ecology.

  • Describe approaches to studying ecology:

    • direct observation of nature

    • manipulative experiments

    • microcosm and lab experiments

    • ecological gradients

    • models

• Ecology - scientific study of the abundance and distribution of organisms in relation to other organisms and environmetnal conditions

• Habitat - place, or physical setting, in which an organism lives

• Potential niche - range of abiotic and biotic conditions that an organisms can tolerate

• Realized niche - range of abiotic and biotic conditions that an organism occurs

• Distribution - geographic area where individuals of a species are present

• Abundance - total number of individuals in a population that exists within a defined area

The Rules of Nature:

• Conservation of energy (including carbon) - energy cannot be created or destroyed, but rather just changes form

• Conservation of mass - mass cannot be created or destroyed, but rather just changes form

• Evolution

• Biotic and abiotic factors limit distribution and abundance

  • Biotic - living factors of an environment (i.e. organisms and interactions between them)

  • Abiotic - non-living factors of an environment (i.e. climate, soil, water availability, and physical conditions)

Hierarchy of Ecological Organization:

• Individual - a living organism

• Population - individuals of the same species living in a particular area

• Community - all populations of species living together in a particular area

• Ecosystem - one or more communities of living organisms interacting with their nonliving physical and chemical environments

• Landscape - multiple ecosystems that are connected by the movement of individuals, populations, matter, and energy

• Biosphere - all the ecosystems on Earth

Interactions Between Species:

Types of Consumers:

• Herbivore - organisms that consume producers

• Predator - organisms that kill and eat other organisms

  • Parasitoid - organisms that lay eggs in or on another animal

• Parasite - live in or on a host organisms

Climate & World Biomes

• Objectives:

  • Distinguish between climate and weather

  • Explain features of Earth-Sun movement and how they influence climate and seasonality

  • Explain features of atmosphere and ocean processes and their function in energy redistribution globally, including:

    • the greenhouse effect

    • the Hadley cell and ITCZ

    • ocean surface and deep currents

  • Describe the world’s major biomes and their relation to climate

• Weather - short-term variation in light, temperature, wind, humidity, etc.

• Climate - long-term average of weather (may include seasonality)

• Albedo - the fraction of solar energy reflected by a surface

• The Earth is tilted 23.5 degrees, causing an uneven distribution of sunlight and causing seasons.

• Earth’s Greenhouse Effect - incoming solar radiation is partially captured and re-emitted by greenhouse gases in the atmosphere, which helps to regulate the planet's temperature, warming the plant and creating a stable environment for life through processes such as trapping heat and reducing temperature fluctuations.

Wavelengths/Electromagnetic Radiation:

• The temperature of a body determines wavelengths of emitted energy.

• Solar radiation his high energy (short wavelength) → penetrates the atmosphere

• Earth emits low-energy (long wavelength) → absorbed by the atmosphere

• Radiations:

  • X & gamma → <300 nm; 1% of total form sun

  • UV → 300-400 nm; 8%

  • Visible → 400-700 nm; 40%

  • Near-Infrared → 700-1500 nm; 40%

  • Lower energy → >1500 nm; 11%

• Hadley Circulation - hot, moist air rising and cool, dry air sinking, causing a circulation of the air

  • Influenced by the Coriolis effect (spinning)

• Cells:

  • Polar Cell - pole to 60 degrees

  • Ferrel Cell - 60 degrees to 30 degrees

  • Hadley Cell - 30 degrees to 0 degree (equator)

• InterTropical Convergence Zone (ITCZ) - is due to uneven heating (tilt/rotation)

  • Shifts seasonally

  • Leads to seasonality of precipitation in many places

  • Two rainy seasons near the equator

• Ocean surface currents transport energy on a short time scale.

• Deep ocean currents transport energy on a large time scale.

  • Thermohaline circulation - ocean water moves due to density differences associated with temperature and salinity

• Atmospheric and oceanic circulation determine climate — energy distribution, redistribution, and resulting global air and ocean circulation control general climate patterns:

  • Tropics are warm and moist

  • 30 degres N and S are dry and hot

  • Poles are dry and cold

  • Europe is warmer than North America at the same latitude

  • Pacific Northwest is cool and moist

  • The Middle East and Saharan Afric are hot and dry

• Convergent Evolution - often caused by a similar climate

• World biomes are determined by climate.

  • The productivity of wold biomes depends on climate.

• 9 Major Biomes:

  • Tundra and boreal forest - plant productivity is energy limited

    • Tundra - short statured herbaceous plants and shrubs

    • Boreal - evergreen and deciduous forest that regularly burns

  • Temperate rainforest and temperate seasonal forest - plant productivity is seasonally energy limited and they are highly productive; evergreen and deciduous forest

  • Tropical Rainforest (jungle) - highly productive and very high biodiversity

  • Savanna - seasonally dry

  • Woodland/shrubland - hot dry summers and mild wet winters; drought tolerant grasses, shrubs, and small trees

  • Temperate Grassland - productivity depends on rain (varies greatly); evolution of grazing

  • Subtropical (Cold) Desert - very dry (sometimes years without rain); plants are highly specialized to deal with drought

Climate Change

• Objectives:

  • Understand forcing agents for climate change including time scales relevant to evolution.

  • Explain the greenhouse effect and how we are changing it.

  • Examine evidence of change in these climate features:

    • surface air T, surface ocean T

    • precipitation, snow cover

    • land and sea ice

    • sea level rise

  • Explain how proxies are used to understand past climate:

    • tree rings, ice cores, ocean sediments

  • Understand that human actions impact future climate (and what models suggest might happen).

• Forcing agents that influence climate:

  • Earth-Sun geometry

  • Greenhouse gases

  • Land-use (albedo) change — how much sunlight is reflected

  • Volcanic activity (sulfur dioxide aerosols)

  • Solar activity (minor changes)

• Greenhouse gases - absorb and emit strongy in the infrared region

  • From most to least important radiative effect — H2O - CO2 - CH4 - N2O - CFCs

  • Observed changes include temperature, precipitation and atmospheric moisture, snow cover, sea level, climate variability and extreme events, and biological systems

• Z-score (standard score) - allows data from different locations to be combined, removes the mean, and scales by standard deviation

  • dimensionless

z=\frac{x-\mu}{\sigma}

z → z-score

x → observed value

\mu → mean of the population

\sigma → standard deviation of the population

• Temperature change is statistically significant.

• The global average air temperature has risn ~1.0 degrees Celcius above the pre-industrial baseline.

• Climate proxy records are derived from:

  • Ice cores - record of past climate

  • Tree rings

  • Historical data

  • etc.

• Milankovitch cycles - change in Earth-Sun geometry

• Currently, due to climate change…

  • glaciers are melting

  • there is a winter snow drought

  • sea ice is decreasing

  • ice caps are melting

  • sea level is rising

  • atmospheric CO2 is rising

• Relative to global net photosynthesis, the scale of fossil fuel energy use is 3 times larger.

• There is a seasonal cycle in atmospheric CO2 due to photosynthesis and respiration of land ecosystems.

Acclimation to Variable Environments

• Objectives:

  • Understand the distinction between regulators and conformers.

    • i.e body T of endotherms and ectotherms

  • Explain phenotypic plasticity.

  • Define and identify homeostasis, acclimation, developmental plasticity, and avoidance.

  • Recognize examples of phenotypic responses to environmental stress such as…

    • physiology/biochemistry

    • morphology

    • behavior

    • avoidance

• Evolution - change in allele trequency of generations

• Phenotypic Plasticity - a single genotype with variation in phenotype

  • Same genes, different traits/characteristics

2 Ways to Cope with a Changing Environment:

Responses to Environmental Variations:

• Homeostasis - maintenance of a nearly constant internal environment within a varying external environment

  • Quick, short-term reversible responses; behavioral

• Acclimation - reversible phenotypic change in an individual organism in response to changing environmenta conditions

  • Long-term (slow) reversible responses

• Developmental Plasticity - differences in phenotypic traits for a given genotypes under different environmental conditions

  • Slow and irreversible

• Avoidance (of adverse environments) - two different types; can be relatively slow or quick and reversible or permanent

  • Migration - seasonal movement of animals from one region to another

  • Dormancy - dramatic reduction of metabolic processes to rely on storage

• Microhabitat - specific location within a habitat that typically differs in environmental conditions form other parts of the habitat

Population Growth & Regulation

• Objectives:

  • Define population ecology.

  • Explain why populations can grow rapidly under ideal conditions.

  • Compare and contrast exponential and logistical population growth.

  • State and interpret the elements of the equations for exponential and logistical population growth.

  • Identify factors that contribute to density dependent growth.

  • Explain carrying capacity.

  • Describe what happens if a population overshoots carrying capacity.

• Population Ecology - the study of how and why the number of individuals in a population changes over time

Exponential Growth Model:

\frac{\Delta N}{\Delta t}=\left(b-d\right)N=rN

N → population size

\frac{\Delta N}{\Delta t} → population growth rate (change in size over time)

\Delta N → change in population size

\Delta t → change in time

b → births per capita

d → deaths per capita

r → per capita population growth rate

• The per capita population growth (r) describes the rate of population change.

• Exponential model:

  • exponential growth → b>d (or r>0)

  • no growth → b=d (or r=0)

  • exponential decline → b<d (or r<0)

• Population size will be regulated or will level at some point in time due to interactions between individuals and the environment (biotic and/or abiotic factors).

• The exponential growth model assumes…

  • essential resources are unlimited.

  • the environment is constant (with minimal predation).

• However, as the density of a population increases…

  • fecundity (birth) decreases

  • mortality (death) increases

Logistical Growth Model:

\frac{\Delta N}{\Delta t}=rN\left(\frac{K-N}{K}\right) → \frac{\Delta N}{\Delta t}=rN\left(1-\frac{N}{K}\right)

\Kappa → carrying capacity of a population

• The carrying capacity (K) describes the upper size limit of a stable population.

• As N approaches K , the term \left(1-\frac{N}{K}\right) approaches zero, slowing population growth.

  • b=d , \frac{\Delta N}{\Delta t}=0

• When N is low relative to K , the term \left(1-\frac{N}{K}\right) is close to 1.0 and the population growth follows the exponential model (rN).

• Density Independent - factors that limit population size regardless of the population’s density

• Overshoot - when a population grows beyond carrying capacity

• Die-off - a substantial decline in density that typically goes well below the carrying capacity

  • K can change depending upon how far the population overshot it and how fast the resource can bounce back.

Carbon is Energy

• Objectives:

  • Understand the importance of photosynthesis for life.

  • Understand the ecological equivalence of energy and organic carbon.

  • Explain the distribution of biomass carbon across taxa.

  • Explain the basic ecosystem carbon cycle (GPP, NPP, respiration).

  • Distinguish autotrophic and heterotrophic respiration.

  • Explain the ecological importance of decomposition.

  • Know that these processes occur in terrestrial and aquatic environments.

Photosynthesis:

6CO_2+12H_2O+light\to C_6H_{12}O_6+6O_2+6H_2O

Major Drivers of Photosynthesis:

• Climate, biome type, and time since disturbance (long-term)

• Sunlight

• Water

• Temperature

• Season length

• Nutrients

• Light is attenuated by water.

• Ocean photosynthesis productivity is the highest in shallow coastal water.

• Photosynthesis rate depends strongly on nitrogen content.

• Worldwide primary productivity depends on the climate.

Carbon Cycle:

NPP=GPP-R_{plant}

GPP → Gross Primary Production (Total Photosynthesis)

R_{plant} → plant respiration

NPP → Net Primray Production (Net carbon gain by photosynthesis after plant respiration)

• NPP varies seasonally.

• Only ~1% of solar energy is converted by photosynthesis (GPP).

  • ~60% is lost to plant respiration, yielding ~40% as NPP.

• NPP is the food/energy source for all living things.

• Autotrophic Respiration - respiration by plants

• Heterotrophic Respiration - respiration by other organisms

• Growth Respiration - the cost of growth is similar among plant species and plant parts

Maintenance Respiration:

R_{plant}=R_{growth}+R_{maint}+R_{ion}

• Maintenance Respiration - cost of maintaining living tissue

  • i.e. protein turnover, membrane repair, etc.

• Rates are primarily controlled by…

  • protein content — high nitrogen tissues have high R_{maint}

  • temperature — high T means high turnover

  • drought — synthesis of osmotic compounds

• Ion uptake respiration (R_{ion}) → the energy cost of taking up ions in the roots

  • Will correlate with NPP

• Respiration rate is directly related to tissue N in plants.

• Decomposition and cycling of organic material occurs in all biomes (both terrestrial and aquatic).

• Decomposition - physical and chemical breakdown of detritus

• Soil Organic Matter (SOM, SOC) - complex mix of dead organic matter

• Labile - organic compound that is easily decomposed (i.e. sugars, aminos)

• Recalcitrant - organic compound that is resistant to decomposition

Trophic Interactions

• Objectives:

  • Understand that ecological communities are functionally structured.

  • Define and recognize consumption, assimilation, production, and trophic efficiency.

  • Contrast assimilation efficiencies of carnivores and herbivores.

  • Contrast production efficiencies of endotherms and ectotherms.

  • Describe the significance of trophic efficiencies in an ecosystem.

  • Explain the concept of keystone species.

• Ecological Community - groups of taxa that interact with each other and the environment

• Community - all populations of different species that occupy a given area, thus interacting either directly or indirectly

consumption efficiency =\frac{I}{P_{n-1}}

• Consumption Efficiency - amount ingested over amount produced by herbivores

assimilation efficiency =\frac{A}{I}

• Assimilation Efficiency - amount digested over amount ingested

• Average animal/bacteria are mostly protein.

• Average plant/algae are mostly carbohydrates.

• Energy flow between trophic levels → assimilation efficiency is higher for animal food than plant food (indigestible cellulose and lignin)

  • Carnivores → ~70-90%

  • Herbivores → ~20-60%

production efficiency =\frac{P_{n}}{A}

• Production Efficiency - conversion of assimilated food into new biomass

  • (growth and reproduction) / (energy assimilated)

• The energy flow between trophic levels (production efficiency) depends on the metabolic rate of the consumer.

  • Ectotherms → ~10-40%

  • Endotherms → ~<5%

trophic (ecological) efficiency =\frac{P_{n}}{P_{n-1}}

• Trophic Efficiency - overall efficiency of energy transfer between trophic levels

  • (consumer biomass) / (prey biomass)

  • percent of energy in the prey that is converted into consumer biomass

  • Average is ~10%

    • ~90% is lost at each trophic level

Biomass & Energy in Terrestrial & Aquatic Ecosystems:

• Terrestrial - most of the energy and standing biomass is in producers

• Aquatic - most of the energy is in producers and most of the biomass is in top predators

  • The relative turnover rate of trophic levels differ.