ecosystems paper 2

define ecology

the study of relationships between organisms and their environment

what does an ecosystem consist of

all living things in an area, swell as non-living physical components that they react with

what are abiotic factors

the non-living physical parts of an ecosystem

give examples of biotic factors

• the number and types of plants and animals

• competition among organisms for essentials such as food, territory and mates

• the dynamics of predator and prey relationships

• the role of diseases and parasites within the eocystem

how might low light intensity influence ecosystems

• photosynthetic organisms may develop larger leaves or use pigments adapted to low light conditions, while organisms that cannot adapt may die

how might warm conditions influence an ecosystem

• plants and ectothermic animals may develop faster, and changes can trigger migration and/ or hibernation in animals, and dormancy and/ or leaf fall in plants

how could low water availability affect an ecosystem

• can lead to drought stress, cellular damage, wilting in plants and reduced photosynthesis rates that can lead to cell death

how can low oxygen availability influence an ecosystem

• suffocation of aerobic organisms, especially those in slow-moving water or waterlogged soils

how can soil type influence an ecosystem

• different soil types, such as sand, loam, and clay have different particle sizes, which affects their drainage properties and the types of organisms they can support

what are trophic levels

stages in a food chain or web that represent the movement of biomass and energy through various organisms

list some key trophic levels

1. producers

2. primary consumers

3. secondary consumers

4. tertiary consumers

5. saprobionts (decomposers)

what are producers

organisms that make their own food e.g. photosynthesising converts light energy into chemical energy

what are saprobionts (decomposers)

organisms that decompose complex materials in dead organisms into simpler substances to obtain their food, and release nutrients back into the ecosystem

what is the difference between a food chain and a food web

a food chain is a sequence of organisms that are connected by feeding, whereas a food web is a complex network of interconnecting food chains within an ecosystem

what do arrows represent in food chains and food webs

the direction of energy flow

define biomass

the total mass of living material present at a particular time in a particular place or within certain organisms. It serves as an indicator of energy content

how can the chemical energy stored in dry biomass be estimated

calorimetry

describe the process of calorimetry to measure biomass

1. dry the biomass sample until its mass remains constant to obtain the dry mass

2. weigh the dry mass

3. burn the dry mass in a calorimeter

4. measure the volume and temperature change of the surrounding water

5. use these values to calculate an estimate of heat energy released from the burnt biomass

what is Gross Primary Production (GPP)

• the total amount of solar energy that plants convert into organic matter

• it is stored as chemical energy within their biomass

what is Net Primary Production (NPP)

• the chemical energy that is available to the next trophic level after accounting for respiratory losses (R)

• it is the energy that is converted into biomass

what is the formula for calculating Net Primary Production

NPP = GPP - R

list factors that contribute to energy loss at trophic levels

1. not all solar energy is captured by leaves or is of the correct wavelength for photosynthesis

2. factors like water availability can limit photosynthesis

3. energy is lost during photosynthetic reactions

4. not all parts of biomass are edible or digestible by consumers

5. energy is lost as heat during movement or respiration

6. energy Is lost in excretory materials, such as urine or faeces

how can agriculture manipulate the transfer of biomass through ecosystems

• it manipulates the environment to favour plant species that we can eat

• it creates simple food chains by reducing the number of trophic levels

• it ensures that as much energy as possible is transferred into biomass that can be eaten by humans 

define ecological efficiency

the efficiency at which biomass or energy is transferred from one trophic level to another (as a percentage)

give the formula for calculating ecological efficiency

ecological efficiency = biomass available after transfer / biomass available before transfer x100

what word can be used instead of biomass in exams

energy

how could we determine the efficiency of energy transfer between trophic levels 

by comparing the net production or net productivity values

what percentage if nitrogen gas makes up the atmosphere

78%

why is the nitrogen cycle useful to organisms

when nitrogen is a gas, it is inaccessible to most organisms.

once it has been transformed into various chemical forms, organisms can use it

list the four key processes in the nitrogen cycle

1. nitrogen fixation

2. ammonification

3. nitrification

4. denitrification

what speed up decay by feeding on detritus 

detritivores (decomposition by detritivores)

what convert nitrogen-containing molecules in dead organisms, faeces and urine into substances like ammonia

saprobionts

what is assimilation by producers like plants

when producers absorb useful substances and incorporate them into other compounds that aid their survival

list some key processes involved in the carbon cycle

photosynthesis, consumption, respiration, decomposition, formation of fossil fuels, combustion, weathering, volcanic activity

what type of fluctuation in carbon dioxide do photosynthesis and respiration cause

daily fluctuation

how are seasonal fluctuations of co2 caused

• During the summer, long daylight hours and warm temperatures increase photosynthesis rates, absorbing more CO₂ and reducing local atmospheric CO₂ levels.

• During winter, reduced daylight hours and colder temperatures decrease photosynthesis rates and resulting in higher local atmospheric CO₂ levels.

how are annual fluctuations in atmospheric co2 caused 

• greenhouse gas emissions

• deforestation

• burning of biomass

what is succession

the process by which ecosystems change over time due to changes in the environment, causing the plant and animal species present to change

what happens as environmental conditions change

different species can colonise, outcompete and replace the species that were previously there

define primary succession

occurs on newly formed or exposed land with no soil or organic matter

define secondary succession 

occurs in areas where an existing community has been removed, leaving the soil intact but with no plant or animal species (e.g. an area which has experienced a forest fire)

list the stages of succession

1. initial colonisation by pioneer species

2. alteration of conditions by pioneer species (they contribute organic matter and help to form soil)

3. settlement by intermediate communities- intermediate species/ secondary colonisers move in when soil improves

4. diversification of intermediate communities- over time, the variety of species and biomass grows, leading to larger and more complex organisms

5. development of climax communities

what are pioneer species

organisms that can cope with extreme conditions such as lichen or algae

what are climax communities

the final stage of succession, where an ecosystem is stable and has a balanced equilibrium of species

list some typical adaptations of pioneer communities

• ability to reproduce asexually

• seeds that are dispersed by wind

• rapid germination

• the ability to photosynthesise

• nitrogen fixation to enrich soil

• extreme condition tolerance

what community (our of pioneer, intermediate and climax) has the fastest growth rate of organisms 

pioneer community

what community has the highest biodiversity

intermediate. climax communities have high biodiversity but they are typically lower than intermediate

what community is the most stable

climax

when does deflected succession occur

when human activity interrupts the normal sequence of succession, preventing the ecosystem from reaching its natural climax community

give some examples of human actions that can cause deflected succession

• continuous grazing or trampling by domesticated animals or livestock

• clearing native vegetation for planting crops

• burning land to clear forests

what are the limitations of using quadrants to measure animal populations

• most animals are mobile and do not remain in a fixed area

• slow moving animals could be counted but fast moving animals may be missed

• organisms could move in and out of the quadrant, so it would not be representative

give some exceptions of where quadrants could be used to sample animals

• with very slow moving animals like barnacles and mussels that are attached to one spot

• where animals are dense and remain within a defined territory

what is a common technique used to estimate the size of animal populations 

mark-release-capture

what can the Lincoln index formula be used for

to estimate total population size based off the recapture data

list some assumptions we make when using the mark-capture-release technique

• the marked individuals distribute evenly amongst the rest of the population

• the population remains constant with no immigration, immigration, deaths or births

• the population has a definite boundary

• the marks are non-toxic and don’t increase predation rates or change behaviour

• the marks are permanent and cannot be lost