2.1: Individuals, Species, Populations, Communities And Ecosystems Flashcards
What is the biosphere?
Refers to the narrow, life-support zone around earth
- where atmosphere; hydrosphere and lithosphere meet
Contains all living organisms
Thought of as one large complex system of:
living communities
Their interactions with one another
Non-living components
-> all interact as one unit
What is a species?
A group of organisms sharing a common characteristic that can interbreed to produce fertile offspring
Members of the same species -> share gene pool -> can breed and produce offspring with similar traits
Explain latin binomials
Genus species (can be shortened to G. species)
-> Genus always capital, species always lowercase
-> when typed - italics
-> when written - underlined
What is a population?
A group of the same species living in the same area at the same time which interbreed
- can be seen as an interbreeding unit of a species
Example of a species with many populations
Eastern grey kangaroo
Marsupials native to Australia
- this species-> multiple populations across Australia
-> Queensland, New South Wales, Victoria, etc. - although individuals from different populations are capable of interbreeding -> very rarely do -> geographically isolated
- each population -> own unique characteristics/adaptations based on local factors
-> habitat, climate and food availability,etc. - despite being part of the same species, these populations may exhibit some small genetic/behavioural differences due to their isolation + local environmental conditions
What is a community?
A community includes all of the different populations (of different species) living in the same area at the same time
Collection of interacting populations within an ecosystem
What is a habitat?
The local environment in which an organism/species/population/community normally lives
Description of habitat can include:
Geographical/physical location
Type of ecosystem needed to meet environmental conditions needed for survival
Different individuals in same species -> can live in diff habitats
Habitats can also change due to migration
What is an ecosystem?
An ecosystem refers to a community of living organisms, along with their physical environment, interacting as a system within a specific area
Includes living/biotic components interacting with non-living/abiotic components
Can vary in size, characteristics
Are open systems -> both energy and matter can move in/out
What are biotic factors?
The living, biological factors that influence ecosystems and the communities of organisms within them
Not just the living things -> also the roles played by each organisms
What are examples of biotic factors?
Availability of food:
More food -> higher chance of survival/reproducing -> population increase
rainforest -> rich food supply -> many species
Desert -> poor food supply -> fewer species
New predators:
Balanced ecosystem -> predators catch enough prey to survive but not so many they wipe out population
New predator -> system becomes unbalanced
Red foxes -> introduced for recreational hunting in Australia (1800s) -> caused decline in native species (small mammals and birds) -> reduced food supply for native predators
New pathogens:
New pathogen -> population living there has no immunity/resistance -> population decline/wipe out
Avian flu -> decline in wild bird species
Outbreak of H5N1 virus in he bar-headed goose in Qinghai lake -> 2005 -> caused death of over 6000 birds (significant proportion of population)
Competition:
Two species compete for same resources -> one better adapted -> that species will outcompete -> can continue until there is too little of non-adapted species to reproduce
NA grey squirrel into UK (1800s) -> decline in native red squirrel population
Grey squirrels outcompeted for resources + carry virus that red squirrels have no resistance to
What are abiotic factors?
The nonliving; physical and chemical factors that influence ecosystems and the communities of organisms within them
Provides essential resources and conditions necessary for the survival and functioning of the biotic community
Changes in abiotic -> affect survival/reproduction of organisms -> affect overall functioning of ecosystem
Examples of abiotic factors
Temp:
Affects rate of photosynthesis, metabolism, growth, reproduction
Some species -> adapted to certain temps
Sunlight:
Required for photosynthesis
More light -> increased photosynthesis -> increased plant growth
pH (soil and water):
Affect availability of nutrients
Influences plant growth + survival of aquatic organisms
Certain species -> adapted to certain pH
Salinity:
Affect the health and survival of aquatic organisms
Certain species -> adapted to certain salinity levels
Dissolved oxygen:
essential for survival of aquatic organisms (esp. fish)
Low oxygen -> hypoxia -> bad for ecosystem
Soil texture:
Influences water retention, nutrient availability, root penetration, plant growth, distribution of soil-dwelling organisms
Moisture and precipitation:
Determines amount of water available to organisms
Impacts survival, growth, reproduction
Minerals and nutrients:
Different species of plants -> adapted to different soil mineral/nutrient contents
Influence plant growth and community composition
Wind intensity:
Wind speed affects transpiration rate in plant, dispersal of seeds/pollen -> affect plant distribution and reproduction
CO2 levels:
CO2 required for photosynthesis
CO2 concentration affect rate and overall plant growth
What is an ecological niche?
A role taken by an organisms within its community
Sum of a species use of the biotic+abiotic resources in an environment
Conditions and resources which an organism or population responds and depends upon
Each species -> own distinct niche
Niche not the same as habitat:
Niche ->organism’s job
Habitat -> address of organism
What is the niche principle?
No two species can occupy the same niche for an extended period of time ultimately one species will always out-compete the other
Two species have identical/similar niche -> cannot live in same habitat ex: Eurasian red squirrel and grey squirrel
-> competitive exclusion
What is population characterized by?
Size
Density
Distribution
Age structure
Growth rate
Interaction with each other
Ecosystems -> many populations of different species interacting with each other
Results in ecological, behavioral, evolutionary consequences
What is herbivory and predation?
HERBIVORY:
Primary consumers feeding only on plants
Carrying capacity of herbivore species -> affected buy the number of plants they feed on
+ plant resources = + carrying capacity
PREDATION:
Consumer that hunts and eats another consumer
Lowers carrying capacity of prey
What is a stable community?
Both prey and predators can have negative feedback effects -> lower carrying capacity of own
Stable community: predator-prey relationship rises and falls in cycles
What is mutualism?
A mutually beneficial, symbiotic relationship
Species usually evolve together
Increases carrying capacity for both species
Ex: bees and flowers
What is parasitism?
A symbiotic relationship where one species lives in or on another
Only parasite benefits, usually damages or kills host
Lower host carrying capacity
Ex: malaria causing parasite
-> infect red blood cells in humans -> recurrent episodes of fever -> can be fatal
Parasite has life cycle that includes mosquito as vessel
What is competition (in terms of population interaction)?
More and more species -> depend on same resources
Can be intra specific (same species):
Lower carrying capacity of population (low food due to high population)
Can be inter specific (different species):
Similar niches species -> decreased carrying capacity of both
Disease in relation to population interaction
Pathogens -> disease
Lower carrying capacity of infected species
Changes in the incidence of disease -> population to fluctuate around their carrying capacity
What is carrying capacity (K)?
Maximum stable population size if a species that an ecosystem can support determined by competition for limited resources
Every individual within species -> potential to reproduce and have offspring to continue population growth
Many abiotic+biotic factors that prevent individuals in a population from adulthood/reproduce
-> makes sure population size of each species is limited -> no domination
-> exception: humans
Definition of density dependent factors
Factors whose impact on population size varies with the population density
-> effect of limiting factor increases as the population increases
Most factors affecting carrying capacity -> density dependent
Ex:
Competition -> food/water availability, space of territories and nesting, availability of mates
Disease, predation, buildup of toxic byproduct of metabolism
Examples of density dependent factors
- competition for resources:
- as population density increases, individuals compete more intensely for limited resources like food, water and shelter
- increased risk of predation:
- higher population density increases the likelihood of predators encountering prey, leading to more predation events
- pathogen transmission:
- dense populations facilitate the spread of pathogens, such as diseases and parasites, leading to increased mortality rates
How do negative feedback back mechanisms effect carrying capacity?
Density dependent factors -> drive negative feedback mechanisms
-> help return population to its equilibrium state -> stability
Ex:
Population density rises -> factors (resource scarcity, increased predation, disease) trigger mechanisms -> reduce population growth rates
What are the two types of population growth curves?
Can be exponential or limited by carrying capacity
no limiting factors -> J curve
Density dependent limiting factors -> S curve
Population growth: J curve
Exponential population growth
Ideal environment required
-> all individuals survive+reproduce
-> resources unlimited (+no competition)
Conditions needed for J curve in nature
-> small population
-> organism just colonize new environment
Jcurve -> growth pattern of population in an environment with unlimited resources
What are the phases of a J curve?
1: lag phase
Initial growth is slow when the population is low
2: exponential growth phase:
Population growth -> accelerates exponentially as population grows
3: crash phase
At some point -> significant population overshoot -> sudden decrease in population
Population growth: S curve
Applies to most populations
Population growth plotted against time -> S shaped curve produced
S population curve -> describe the growth pattern of a population in a resource limited environment
What are the phases of an S curve?
1: lag phase
Initial growth is slow (population small)
Little to no growth -> period of adaptation/prep for growth
2: exponential growth phase
Low or reduced limiting factors -> exponential growth
Births > deaths
-> + reproduction
-> cannot last forever
3: transitional phase
Population grows -> increased competition between individuals for same limiting factors/resources
4: plateau phase
Population reaches carrying capacity -> fluctuates around a set point determined by the limited factors
Changes in limiting factors -> changes in population size (fluctuate around K) -> controlled by negative feedback
K exceeded dramatically -> death
How do limiting factors affect human population?
Humans special -> we can overcome limiting factors
-> means negative consequences for sustainability
Reasons we can overcome:
Elimination of natural predators:
-> imbalance in ecosystems
-> ex: over grazing by deer due to absence of wolves
Technological advances:
-> agriculture and medicine -> less deaths and more food
-> exponential population growth
Degradation of the enviroment
-> Extract valuable resources
-> deforestation -> agriculture and urbanization
-> disrupts ecosystems -> habitat destruction, pollution, resource delopetion
Why is it difficult to assess human carrying capacity?
Broad and changing ecological niches of humans
-> technological advancements that modify environment and overcome traditional K limitations
-> cultural and social factors influence population dynamics (migration)
-> changing lifestyles and consumption patterns -> impact demand and impact
-> adaptive capacity -> innovate response to change -> influence resource use/efficiency and tech development
-> Urbanisation and industrialization -> reshape human habitats
Estimates disputed -> uncertainties in many factors
Overall because:
We use more resources than any other
We substitute resources and use of resources varies between individuals
Import/export
Tech developments
What are the advantages and disadvantages of looking at the entire population during a study?
Advantage:
Accurate results
-> every member is used and all options will be included
Disadvantage:
Time consuming
Expensive -> large numbers and large amount of data to organize and analyze
What are the advantages and disadvantages of looking at a sample of a population during a study?
Sample -> selected part of the population
-> random or biased
Advantages:
Quicker
Cheaper
Less data to organize and analyze
Disadvantages:
Unreliable results
Introduce bias
Might not represent all of population
What are 2 different types of sampling strategies?
Random -> chance
random number generator
No bias
Can be used with small-ish population -> all individuals have a equal change of being samples
Systemic -> chosen by regular pattern
Some bias
Unrepresentative of the whole area
Random is usually better
What is transect sampling?
Systemic sampling-> transect sampling used when there is a clear change in the physical conditions across the area being studied
-> take samples along a line that extends away from or along an environmental feature
—> transect
Transects -> help show how species distribution changes with the different physical conditions
Ex: changes in altitude, soil pH, light intensity
What are two types of transects?
Line transects:
Lay out measuring tape in a straight line across the sample area
Equal distances along tape -> record identity of the organism that touches the line
Belt transect:
Place quadrats at regular intervals along tape
Record abundance.percentage cover of each species within each quadrat
What is quadrat sampling?
Quadrat placed on ground and organisms within recorded
Usually used for non-motile organisms (plants)
Used to estimate population size by recording:
Number of individuals
Percentage cover
Used to compare populations of species in same/different areas
Key concepts:
Sample chosen at random
Number of samples -> statistically significant
Quadrat sampling: how to estimate population size
- Use two tape measure to lay out survey area in chosen habitat
- Use random number generator to create set of coordinated to place first quadrat
- Count number of your chosen plant species in quadrat
- Record this number in a results table and repeat previous steps
- Estimate the population by using this equation:
Estimated population size = (total area/sampled area) x total number of organisms
Quadrat sampling: estimating percentage cover and percentage frequency
Percentage cover -> an estimate of the area within a given quadrat covered by the plant or animal being sampled
Percentage frequency -> number of squares in which the species occurs divided by the number of possible occurrence
-> % frequency = (number of quadrat squares in which species present/total number of quadrat squares) × 100
Useful when it is difficult to count individual plant organism
Repeated over series of quadrats to calculate average
What is the Lincoln index?
A method used to estimate the abundance or population size of a species in a given area
Usually used alongside capture-mark-release-recapture method
For motile organisms
How is the Lincoln index used?
First capture-mark-release-recapture technique:
Large sample taken -> counted and marked in a way that won’t affect survival
Marked individuals -> returned to habitat and randomly mix with population
Sufficient amount of time passed -> another large sample captured
Number of marked and unmarked recorded
Proportion of marked to unmarked -> used to calculate estimated population size (Lincoln index)
Formula for Lincoln index:
Estimated population size = (number of individuals caught in sample 1 x number of individuals in sample 2) / number of marked individuals in sample 2
What are the limitations of the Lincoln index/the capture-mark-release-recapture method?
Marked individuals must be given enough time to mix -> time consuming
Marking shouldn’t affect survival
Marking must remain visible
Population must stay the same size
-> births/deaths of individuals affect data
What are dichotomous keys?
Tools used to identify organisms based on their characteristics
Series of paired statements/questions
What are the limitations of dichotomous keys?
Limited scope:
Designed to identify a limited number of species
May not be comprehensive enough
Inaccuracies:
Only as accurate as info provided
Not designed well -> identifications inaccurate
Variability:
Organisms have variable physical characteristics
Time consuming:
Especially for beginners who are unfamiliar with organisms
Expertise required:
Certain level of expertise/familiarity to organisms being identified
Limited to physical characteristics:
Doesn’t take into account behaviors, habitat, etc which can be crucial in identifying certain species
What is sustainability?
Ecosystems ability to maintain balance and productivity over time
Ecosystems natural regulate themselves to sustain life within them
What is a steady state ecosystem? How can this be illustrated?
Inputs + outputs -> balanced
Inputs include:
Energy
Nutrients
Water
Outputs include:
Energy
Nutrients
Waste
Balance -> long term stability + resilience
Can be illustrated with ecosystem flow diagrams
- demonstrate movement of energy and nutrients in ecosystem
- highlight interconnectedness of bio + abio factors
What is a keystone species?
A species that plays a critical role in maintaining structure of an ecological community
Impact larger than expected
- critical for health + long term stability
-> regulate population size, help maintain high biodiversity - removal of keystone: cascading effects
-> significant change in community structure + function
-> disrupt balance too much: increase risk of ecosystem collapse - difficult to identify importance -> usually only seen after they are lost
What is biosphere integrity?
Planetary boundary: Refers to the overall health and diversity of life on earth
Human activity -> significantly impacted biosphere integrity -> push beyond critical thresholds
Disturbance to ecosystems ->
- severe loss of biodiversity
- disrupt ecological balance/resilience
Ecosystem + species diversity -> highly interlinked
- health ecosystem support diverse species populations
- diverse community contribute to ecosystem resilience + stability
Loss of biodiversity due to human activity -> undermine integrity of ecosystem -> more vulnerable
