Lecture 4 Flashcards
What are the 3 main areas of study in ecology
- the distribution and abundance of all organisms
- the interactions among living organisms (= biotic factors)
- the interactions between living organisms and their non-living surrounding environments (= abiotic factors)
What 2 factors are complex systems made up of
species and their interactions with physical and chemical surroundings
Define habitat
The physical environment in which individuals of a species can be found
Define niche
The role a species plays in its community
- e.g how it gets NRG/nutrients
- habitat requirements
What are the levels of study in ecology
- Biosphere (global processes)
- ecosystem (NRG flux, cycling nutrients)
- community (interactions among populations)
- population (population dynamics the unit of evolution)
- organism (survival and reproduction; the unit of natural selection)
Define population
a group of individuals belonging to one species that live in a particular area at the same time and where they share resources
Define population dynamics
Changes in population over time
What factors affect population dynamics
- size
- density
- distribution or dispersion
- demographics
- sex ratio
- age structure
- survivorship
Define size (population dynamics)
Number of individual organisms present in a location at one given time
Define minimum viable population
smallest number of individuals that would still allow a population to persist or grow ensuring long-term survival
Define density (pop. dynamics)
Number of individuals within a population per unit space
What happens when populations are too low
- normal social behaviors are deficient
- unable to find mates/ mating behaviors don’t occur
- genetic diversity falls
- important community connections may be lost, affects other species
What happens if population density is too high
- normal social behaviors breakdown with overcrowding
- disease spread increases
- low food supply
- increased human conflict
- overuse of resources -> damage to environment
Define distribution (dispersion)
Spatial arrangement of individual organisms within an area
What are the 3 types of distribution
Clumped (common)
- based on resources or habitat
- animals
Random
- resources found throughout habitat with little competition
- plants
Uniform
- individuals compete for resources and space
- plants, nesting birds
Define demographics
Response to changes in sex ratio, age structure, survivorship
Define sex ratio
proportion of males to females
- monogamous species, a 50/50 sex ratio is optimal
Define age structure
relative numbers of individual organisms in each age cohort within a population
What are the 4 types of age structures
- increasing rapidly
- increasing slowly
- stable
- decreasing
Define survivorship
patterns of survival at different life stages
- Crude estimation of birth/death rates
What are the 3 types of survivorship
Type I: few deaths at younger ages with most deaths at older ages
- humans
Type II: equal number of deaths at all ages
- birds
Type III: more deaths at younger ages and fewer deaths at older ages
- amphibians (frogs)
What are the 4 factors involved in population growth
Additions:
1. birth
2. immigration
Subtractions:
1. deaths
2. emigration
What are the 2 growth models
- exponential growth model
- logistic growth model
What is the exponential growth model
Steady growth rates (= r) cause exponential growth
- gives a “J-shaped” curve
- assumes unlimited resources
- cannot be sustained indefinitely
- e.g small populations growing under ideal conditions
What is the logistic growth model
Growth rates slow down as resources become limiting as the carrying capacity is approached
- results in an s-shaped curve
- carrying capacity is important
- Occurs commonly in nature with large stable populations
What are the 2 types of pressures that affect the logistical growth model
- Biotic pressures (predation, disease, competition) = resistance factors
- Abiotic pressures (habitat, light, nutrients, water) = growth factors
What are some factors that control population growth
- With density-independent factors (= random factors)
birth rate and death rate do not change with population density
- weather phenomena, natural catastrophes, random events - With density-dependent factors (or resistance factors)
- populations are controlled by factors that regulate growth through negative feedback mechanisms that keep the population size
What are the 6 mechanisms that affect density-dependent factors
- competition for resources (e.g. food, water, space)
- territoriality
- predation
- health (e.g. spread of disease)
- toxic waste accumulation
- intrinsic factors – species specific
What are the 2 growth categories
- r-selected Species
- controlled by reproductive or growth ability of species (or r)
- have a high biotic potential (high r) - . K-selected Species
- controlled by carrying capacity of habitat (or K)
- have a low biotic potential (low r)
What are some characteristics of r-selected vs. k-selected species
- short vs. long life
- slow vs. rapid growth of individual
- early vs. late maturity
- many small vs. few large offspring
- little vs. high parental care
- adapted to unstable vs. stable environments
- prey vs. predators
- niche generalists vs. specialists
What are some examples of r vs. k selected species
r:
- dandelions, spotted knapweed, deer mice
k:
- elk, spruce trees, bears
How do population changes affect communities
- As population in one species declines, other species appear
What are some challenges to protecting biodiversity
- Social and economic factors affect species and communities
Define community
a group of populations of different species living in the same place at the same time
What are the 4 types of interactions
(-/-), (+/-), (+/+), (+/0)
Define (-/-) interactions
- interactions can be detrimental to both species
- competition
Define (+/-) interactions
- beneficial to one species, detrimental to the other
- predation
- herbivory
- parasitism
- disease
Define (+/+) interactions
- interaction beneficial for both species
- mutualism
Define (+/0) interactions
- one species benefits the other is unaffected
- commensalism
Define resource partitioning
- Occurs when species divide shared resources by specializing in different ways
- e.g one species active at night the other in the day
What is intra vs. inter specific competition
Intraspecific Competition
- between members of the same species (in a population)
Interspecific Competition
- between members of 2 or more different species (in a community
Define feedback loop
a system’s output serves as input to the system
Define negative feedback loop
- drifts away from set-point but the system returns
- keeps populations at or below the carrying capacity
What are the trophic/ feeding levels
- indicate role in feeding hierarchy
- producers – produce food from sunlight (photosynthetic)
- consumers – consume other organisms (herbivores, carnivores)
- decomposers – breakdown organic matter (dead organisms) and recycle nutrients
How many kinds of consumers are there
3
primary, secondary, tertiary
Define food chain
relationship of how energy is moved through trophic levels (linear)
What’s 10% rule
only 10% of energy and matter at one trophic level is available to be used by the next higher trophic level
Define food web
- a more realistic visual map of all feeding relationships in a community
- some species can have more than one role depending on trophic level(s) involved
Define ecosystem engineers (foundation species)
- some organisms exert their influence by causing physical changes in environment that affect community structure
- e.g beaver dams
Define keystone species
- Have a strong or wide-reaching impact far out of proportion to its abundance
- Removal of a keystone species has substantial ripple effects
alters food chain
Define invasive species
- A species that spreads widely and rapidly becoming dominant in a new community that changes a community’s functioning
- Many invasive species are non-native, introduced from other areas - have no natural controls (e.g. predation, disease, competition) in invaded area
- e.g zebra mussels
Define aquatic biomes
- Aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth
- Freshwater (lakes, rivers)
- salt concentration of less than 1%
- linked to terrestrial biomes
- Saltwater (oceans, estuaries)
- salt concentration ~3%
- cover about 75% of Earth’s surface
- have enormous impact on the biosphere
Define terrestrial biomes
- Involve assemblages of similar communities, distinguished by the dominant plant type and vegetation structure
- Determined by varying climate (e.g. precipitation and temperature)
What are the 12 major terrestrial biomes
- temperate deciduous forests
- temperate grasslands
- temperate rainforest
- tropical rainforest
- tropical dry rainforest
- savanna
- desert
- tundra
- boreal forest
- chaparral
- mountainous regions
- unvegetated regions
What are major terrestrial biomes defined by
- mean annual precipitation
- mean annual temperature
Define community succession
predictable series of changes in a community following a disturbance
define primary succession
- a disturbance that eliminates all vegetation and soil (e.g. dried lakes, glaciers, volcanic lava)
- colonized by r-selected species that start to rebuild soils
Define secondary succession
- a disturbance (e.g. fires, hurricanes, farming, logging) that alters, but does not destroy, all local organisms
- soil is not lost
Define climax community
- mature community resulting from completed succession series
- involves K-selected species
What is the problem with the ecosystem approach to environmental problems
- Environmental entities are complex systems (= ecosystems) that interact with each other
- To solve environmental problems, all systems must be considered
– leads to overwhelming complexity
How do ecosystems function
- Energy flows through ecosystems in one direction
- energy from the sun enters ecosystems where it is processed, transformed and used with waste energy leaving as heat (entropy - Matter recycles within ecosystems repeatedly
- outputs from some organisms are used as inputs by other organisms - nothing is wasted
Define the law of minimum
For every population there will be a limiting resource which determines the carrying capacity of the habitat
What are some limiting resources for the law of minimum
- physical factors (temperature, geology, light, water availability)
- chemical factors (pH, salt, nutrients, contaminants, etc.)
- biological factors (competition, cooperation, disease, parasites, etc.)
What are biogeochemical cycles
refer to nutrient cycles
What are the 3 different types of nutrients
- Nutrients = elements and compounds required for survival that are consumed by organisms
- Macronutrients = nutrients required in relative large amounts (e.g. carbon, nitrogen, phosphorus)
- Micronutrients = nutrients (e.g. calcium, copper, iron, sodium, magnesium, zinc) needed in smaller amounts
Define reservoirs
where large amounts of nutrients are stored
Define sources
release more nutrients than they accept
Define sinks
accept more nutrients than they release
Define
movement of nutrients among reservoirs
What are the 3 nutrient cycles
- Carbon
- Phosphorus
- Nitrogen
What are the 2 carbon cycles
- fast cycle (biological)
- slow cycle (chemical, geological, physical)
What are some human affects on the carbon cycle
- burning fossil fuels
- forest fires
- deforestation
What are some human affects on the phosphorus cycle
- open-pit mining
- animal waste
What are some affects humans have on the nitrogen cycle
- fertilizing
- burning fossil fuels
Define habor-bosch process
synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia
- dramatically changed the nitrogen cycle
- humans are fixing as much nitrogen as nature does
Define eutrophication
process of nutrient over-enrichment that leads to blooms of algae, increased production of organic matter, and ecosystem degradation
What are the steps of eutrophication
- nitrogen input
- phytoplankton flourish at the surface
- dead phytoplankton and their waste drift to the bottom, providing more food for decomposers
- decomposer population grows and consumes more oxygen
- insufficient oxygen suffocates fish and shrimp at the bottom; dead zone (hypoxic zone) forms
How has excessive nutrients devastated aquatic systems
- phosphorus inputs from sewage and fertilizer runoff that led to eutrophication
- pollution and human impact have devastated fisheries and altered marine ecosystems especially from nitrogen runoff
- dead zones have appeared along coastlines as a result of pollution from farms, cities, and industry (= eutrophication)
