2.1: Individuals, Species, Populations, Communities And Ecosystems

Question 1

What is the biosphere?

Answer 1

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

Question 2

What is a species?

Answer 2

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

Question 3

Explain latin binomials

Answer 3

Genus species (can be shortened to G. species)

-> Genus always capital, species always lowercase
-> when typed - italics
-> when written - underlined

Question 4

What is a population?

Answer 4

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

Question 5

Example of a species with many populations

Answer 5

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

Question 6

What is a community?

Answer 6

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

Question 7

What is a habitat?

Answer 7

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

Question 8

What is an ecosystem?

Answer 8

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

Question 9

What are biotic factors?

Answer 9

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

Question 10

What are examples of biotic factors?

Answer 10

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

Question 11

What are abiotic factors?

Answer 11

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

Question 12

Examples of abiotic factors

Answer 12

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

Question 13

What is an ecological niche?

Answer 13

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

Question 14

What is the niche principle?

Answer 14

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

Question 15

What is population characterized by?

Answer 15

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

Question 16

What is herbivory and predation?

Answer 16

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

Question 17

What is a stable community?

Answer 17

Both prey and predators can have negative feedback effects -> lower carrying capacity of own

Stable community: predator-prey relationship rises and falls in cycles

Question 18

What is mutualism?

Answer 18

A mutually beneficial, symbiotic relationship
Species usually evolve together

Increases carrying capacity for both species

Ex: bees and flowers

Question 19

What is parasitism?

Answer 19

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

Question 20

What is competition (in terms of population interaction)?

Answer 20

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

Question 21

Disease in relation to population interaction

Answer 21

Pathogens -> disease

Lower carrying capacity of infected species

Changes in the incidence of disease -> population to fluctuate around their carrying capacity

Question 22

What is carrying capacity (K)?

Answer 22

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

Question 23

Definition of density dependent factors

Answer 23

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

Question 24

Examples of density dependent factors

Answer 24

• 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

Question 25

How do negative feedback back mechanisms effect carrying capacity?

Answer 25

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

Question 26

What are the two types of population growth curves?

Answer 26

Can be exponential or limited by carrying capacity

no limiting factors -> J curve
Density dependent limiting factors -> S curve

Question 27

Population growth: J curve

Answer 27

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

Question 28

What are the phases of a J curve?

Answer 28

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

Question 29

What are examples of J curve population growth?

Answer 29

Bison:
1800 -> decimated by hunters
1889 -> only 1000 bison

US gov and private landowners -> establish protected herd in late 1800 - early 1900

Herd started small -> plentiful resources+little predators -> grew quickly

the bison population in northern Yellowstone national park increased from 21 in 1902 to 250 in 1915

Cane toad:
Invasive species -> introduced to ecosystem and outcompetes native species -> exponential growth

Toad -> Australia to control agricultural crop pest on sugar cane
-> now invasive -> reproduced so heavily -> toxic secretion+skin -> threat to native species

Australians -> instructed to kill

Humans:
Population exploded -> will have to reach limits -> negative feedback mechanism

Question 30

Population growth: S curve

Answer 30

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

Question 31

What are the phases of an S curve?

Answer 31

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

Question 32

How do limiting factors affect human population?

Answer 32

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

Question 33

Why is it difficult to assess human carrying capacity?

Answer 33

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

Question 34

What are the advantages and disadvantages of looking at the entire population during a study?

Answer 34

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

Question 35

What are the advantages and disadvantages of looking at a sample of a population during a study?

Answer 35

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

Question 36

What are 2 different types of sampling strategies?

Answer 36

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

Question 37

What is transect sampling?

Answer 37

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

Question 38

What are two types of transects?

Answer 38

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

Question 39

What is quadrat sampling?

Answer 39

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

Question 40

Quadrat sampling: how to estimate population size

Answer 40

1. Use two tape measure to lay out survey area in chosen habitat
2. Use random number generator to create set of coordinated to place first quadrat
3. Count number of your chosen plant species in quadrat
4. Record this number in a results table and repeat previous steps
5. Estimate the population by using this equation:
   Estimated population size = (total area/sampled area) x total number of organisms

Question 41

Quadrat sampling: estimating percentage cover and percentage frequency

Answer 41

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

Question 42

What is the Lincoln index?

Answer 42

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

Question 43

How is the Lincoln index used?

Answer 43

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

Question 44

What are the limitations of the Lincoln index/the capture-mark-release-recapture method?

Answer 44

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

Question 45

What are dichotomous keys?

Answer 45

Tools used to identify organisms based on their characteristics

Series of paired statements/questions

Question 46

What are the limitations of dichotomous keys?

Answer 46

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