Ecology Flashcards
Ecology
-Ecology is the study of interactions organisms have with each other and with their environment
-Levels of Ecological Study:
Organism
Population
Community
Economy
Evolutionary
Organismal Ecology
-Physiological Ecology: normal (bodily) functions
Population Ecology
- Population: a group of individuals of the same species living in the same area
- Population ecology focuses primarily on factors that influence population density, growth, and dispersion
Community Ecology
- Community: an assemblage of interacting species in the same geographic area
- Community ecology is generally concerned with the interactions among population that affect the distribution and abundance of species within the community
Ecosystem Ecology
- Ecosystem: a system that includes a biotic community and its abiotic environment
- Ecosystem ecologists tend to focus on the flow of energy and matter through organisms and their environment
Evolutionary Ecology
- Evolution: genetic changes in a population over time
- Evolutionary ecology combines population ecology and population genetics to look at the affect of ecological interactions on the evolution of a population
Conservation Biology
Attempting to maintain biological diversity
Restoration Ecology
Restoration and management of disturbed ecosystem
Landscape Ecology
The study of spatial patterns in the landscape and how they may be impacted by human activities
Biosphere
- The biosphere includes all living things on earth
- The major types of ecosystems found on earth can be divided into biomes based on the types of vegetation that live there
- The vegetation found in a particular ecosystem is largely determined by climate
Factors that Influence Climate
- Unequal heating of Earth’s surface
- Seasonality
- Proximity to the ocean, and west/east coast differences
- Orographic Effect: the effect of mountain ranges
Tropical Rainforests
- Most occur within 20 degrees latitude of equator
- Little temperature variation between months
- Annual rainfall of 2000-4000 mm relatively evenly distributed
- Quickly leaches soil nutrients
- Mycorrhizae help gather nutrients
- Trees and vertical dimension
Tropical Dry Forest
- Usually located between 10-25 degrees latitude
- Climate more seasonal than tropical rainforest
- Soils generally richer in nutrients, but vulnerable to erosion
- Shares many animal and plant species with tropical rainforests
- Heavily settled by humans with extensive clearing for agriculture
Tropical Savanna
- Most occur north and south of tropical dry forests within 10-20 degrees of the equator
- Climate alternates between wet/dry seasons
- Drought associated with dry season leads to lightning-caused wildfires
- Soils have low water permeability
- Saturated soils keeps trees out - Landscape is more two-dimensional with increasing pressure to produce livestock
Desert
- Major bands at 30 degrees N and 30 degrees S latitude
- Occupy about 20% of earth’s land surface
- Water loss usually exceeds precipitation
- Soil usually extremely low in organic matter
- Plant cover ranges from spares to absent
- Animal abundance low, but biodiversity may be high
- Strong behavioral adaptation
Chaparral
- Found in Mediterranean climates
- Occur in all continents except Antarctica
- Climate cool and moist in fall, winter, and spring, but can be hot and dry in summer
- Fragile soils with moderate fertility
- Trees and shrubs typically evergreen
- Fire-resistant plants due to fire regime-plants grow back quickly after they burn
- **The biome we live in
Temperate Grassland
- Extremely widespread distribution
- Annual rainfall 300-1000 mm
- Experience periodic droughts
- Soils tend extremely nutrient rich and deep
- Thoroughly dominated by herbaceous vegetation
- Large roaming ungulates
- Bison vs. Cattle
Temperate Forest
- Old Growth: native forests (we didn’t plant the trees)
- Majority lie between 40 and 50 degree latitude
- Rainfall averages 650-3000 mm
- Fertiles soils
- Long growing seasons dominated by deciduous plants (drops leaves)
- Short growing seasons dominated by conifers (cone, needle like)
- Biomass production can be very high
Boreal Forest (Taiga)
- Confined to Northern Hemisphere
- Covers 11% of Earth’s land area
- Thin, acidic soils low in fertility
- Generally dominated by evergreen conifers
- Relatively high animal density
Tundra
- Covers most lands north of Arctic Circle
- Climate typically cool and dry with short summers
- Low decomposition rates
- Supports substantial numbers of native mammals
Population Ecology
-Population: An interacting group of individuals of the same species that use common resources and lie in the same area
-Population ecologist focus on the factors that affect the distribution and abundance of individuals in a population
-The distribution and abundance of individuals is characterized by many factors:
Density, Dispersion, Size, Growth rates, Age structure, Life History
Population Density
- Population density is the number of a species per unit area or volume
- Density is often related to the dispersion of individuals in a population
- Population density can fluctuate based on habitat stability
Population Dispersion
- Dispersion patterns refers to the way individuals are spaced in their geographic area
- Patterns can be described in three ways:
- Clumped distribution, Uniform distribution, Random Distribution
- Populations can be clumped, uniform or random at small scales, but at larger cales, dispersion patterns are almost always clumped
Clumped Distribution
Individuals are attracted to each other or a resource
Uniform Distribution
Individuals are about the same distance apart from each other
Random Distribution
The distance from one individual to the next is fairly unpredictable
Distribution vs. Dispersion
- Distribution: groups of things
- Dispersion: individuals
Population Size
- Population size refers to the total number of individuals in a population, regardless of density or dispersion
- How can you determine population size?
- Direct count (census): only possible for small populations- Statistical estimation: ex. Mark-recapture
Assumption in Mark-Recapture
- Markig has no effect on mortality/survivability of the individuals
- Marking has no effect on likelihood to being captured
- There is no immigration or emigration between sampling times
- Equal capture probability
- *Any method for population size has assumptions
- **The reliability is only as good as the assumptions made
Changes in Populations Size
- Immigration adds individuals
- Emigration subtracts individuals
- Briths adds individuals
- Deaths subtract individuals
Population Growth
- Modeling is a method of summarize information and processes in an informative manner (ex. caricature)
- Two common and useful models in population ecology:
- Exponential growth (J-curve)
- Logistic growth (S-curve)
Exponential Growth
- The population multiplies by a constant factor during constant time intervals
- G=rN
- r (per capita growth rate) is assumed to be constant, meaning that population growth rate (G) depends solely on the population size (N)
- Long periods of exponential growth are unrealistic
Effects of Death
-Population will grow exponentially as long as per capita death rates are lower than per capita birth rates
Density Dependent Factors
- In nature, a population may grow exponentially for a while, but eventually one or more environmental factors will limit its growth
- Population-limiting factors restrict population growth
Logistic Growth Model
- Modified version of exponential growth that allows population growth to be slowed by limiting factors
- Example of limiting factors: food, space, nesting sites, waste build-up
- G=rN[(K-N)/K]
- K carrying capacity (number of individuals that can be supported by the environment)
What Factors Limit Population Growth?
-Density-dependent factors:
-lack of food
Predation: the more prey, the more they’ll get eaten
-Competition
-Waste products
-Nesting sites
-Diseases
-Density-Independent Factors:
-Climate
-Catastrophe
Density-Dependent Factors
- Population-limiting factors whose effects intensify as the population increases in size
- Increase a population’s death rate or decrease the birth rate
- In many natural population, density-independent factors limit population size before density-dependent factors become important
Complex Patterns of Population Growth
- Some populations have growth patters that don’t fit well into an exponential or logistic model
- One example of a complex pattern is the cycles that frequently occur between predator and its prey
- Boom-and-bust cycles of the snowshoe hare and one of its predators the lynx
- These cycles are the result of many factors, in including predation and plant defenses
Human Population growth
- Exponential so far
- Age structure differs greatly between developed and developing nations
Life Histories and Their Evolution
-Life history traits are those that affect a population’s schedule of reproduction and death
-Environmental factors shape the life history of species through natural selection
Survivorship curves and life tables allow ecologists to compare life history traits among populations and species
Life Table
- Tracks age-specific patterns
- Population is divided into age categories
- Birth rates and mortality rists are calculated for each age category
Survivorship Curves
- Survivorship curves show the age-specific survivorship of a population
- What do they tell us about life history?
- life history: the timing of reproductive and other important life events
Communities
- A community consist of ll the populations of organisms living together and potentially interacting in a particular area
- Ecologists often asses four important factors in a community:
- Diversity, Dominant organisms, Stability, Trophic structure
Diversity
- Diversity refers to the variety of species present in the community, and is measure in two ways:
- Species richness (the number of different species)
- Evenness (the relative abundance of individual species)
Dominant ORganisms
- The type of organisms that dominate a community can give great insight into the processes taking place within the community or ecosystem
- Ex. Type of vegetation can be indicative of rainfall or grazing rates; size of predominant zooplankton can suggest the type of fish around in a lake
Stability
-Community stability is the ability to resist change and return to the original species composition and structure following a disturbance
-Disturbances are episodes that damage biological communities, destroy organisms, and lather the availability of resources
Ex. fire, storms, drought, hard frost
Succession
- Change in the composition of a community over time
- Succession can follow a disturbance and return a community to its former state
Types of Succession
- Primary succession: the formation of a community in a new environment where a community has never been
- Secondary succession: the replacement of communities that were destroyed or displaced
Pioneer Species
- Species that colonize barren habitats
- Lichens small plants with brief life cycles
- improve conditions for other species who then replace them
Climax Community
- Stable array of species that persists relatively unchanged over time
- Succession does not always move predictably toward a specific climax community other stable communities may persist
- Cyclic and small-scale changes also shape community structure
- Tree falls cause local patchiness in tropical forests
- Fires periodically destroy underbrush in sequoia forests
Keystone Species
- A species that can dictate community structure
- Removal of a keystone species can cause drastic changes in a community; can increase or decrease diversity
Trophic Structure
- Trophic structure refers to nutritional relationships among members of the community
- The trophic structure of a community determines how energy and nutrients pass from one link to another (trophic levels) in the food chain/web
Food Chain
- The sequence of food transfer from trophic level to trophic level
- May have many levels
Food Webs
- The feeding relationships in an ecosystem
- Are typically not as simple as in an unbranched food chain
- Are usually woven into complex food webs
Interspecific Competition
- Occurs when a shared resource is limited
- Competition inhibitts the growth of both populations and can result the competituve exclusion of one species
- Ex. Gause’s experiemtn with paramecium
- Competitive exclusion principle says that two species with very similar niches cannot coexist
The Ecological Niche
- A species’ ecological niche
- IS the sum total of a specie’s use of the biotic (relating to living things) and abiotic (not derived from living things) resources in its environment
- Is the specie’s ecological role
Resource (Niche) Partitioning
- There are two possible outcomes of competition between species with identical niches
- Extinction of one species
- Evolution of one species to use a different set of resources (=niche partitioning)
Predation
- Predation is when one organism consumes another
- Predation (including herbivory) is responsible for moving energy through the community
- Predation can play a large role in the evoltion of species, causing plants and animals to develop mechanisms to escape predation
Ways to Escape Predation
-Increase size or speed
-Behavioral defneses
-Hide (camouflage or cryptic behavior)
Mimic somethin that is not good to eat
-Defensive structures (Spines, armor, etc.)
defensive chemicals
-Coevolution occurs when predator and prey evolve reciprocal adaptations to counter chagnes in the other
Predation and Species Diversity
- Predator-prey relations can actually preseve species diversity
- The experiment of Rober Paine
- Removed a dominant predator from a community
- Provided evidence of the phenomenon of keystone predatore
Keystone Predators
-Help maintain species diversity by preventing competitive exclusion of weaker competitors
Symbiosis
- A symbioitic relationship si when two or more species live in, on, or with each other
- Types of Symbiosis:
- Parasitism (+/-) ex. tapeworm
- Commensalism (+/0) ex. eyelash mites
- Mutualism (+/+) ex. ants and acaica
Parasitism
- IS a symbiotic relationship in which one organism benefits whil the other is harmed
- The parasite obtains its nutrients by living in or on its host organism
Mutualism
-IS a symbiosis that benefits both partners
-Indirect Mutualism
-Some organisms are mutually beneficial because of the relationship with a third species
Commensalism
-One species benefits, the other is unaffeected
Ecosystem
An assocuation of organisms and their physical environment, inteconnected by ongoing flow of energy and a cycling of materials
Modes of Nutrition
- Autotrophs:
- Capture sunlight or chemical energy
- Producers
- Heteroptrophs:
- Extract energy from other organisms or organic wastes
- Consumers
Consumers
Herbivores Carnivores Parasites Omnivores Decomposers Detrivores
Trophic Levels
- All the organisms at a trophic levels re the same number of steps away from the energy input into the system
- Producers are closest to the energy input and are the first trophic level
Food Chain
- A striaght line sequences of who eats whom
- Simple food chains are rare in nature
Energy Losses
- Energy transfers ar never 1-% efficient
- Some energy is lost at each step
- Limits the number of trophic levels in an ecosystem
