ecology Y13

What is ecology?

The study of the interrelationships between organisms and their environment

What are examples of abiotic factors?

• temperature

• Light

• Water

• Nutrients (nitrates and phosphates)

What are examples of biotic factors?

• competition

• Predation

• Disease

What is the order of the levels of organization of the environment?

What is an ecosystem?

All the organisms living in a particular area and all the abiotic conditions found there

What is a habitat?

A place in the ecosystem inhabited by a population

What is a biome?

A major type of community

What is a biosphere?

All of the earth including all the ecosystems and communities

What is a community?

All the populations of all the different species living and interacting together in a habitat

What is a population?

The number of individuals of a species in a place

What is an ecological niche?

How an organism perfectly fits into its environment and what it needs for survival

What is carrying capacity?

The maximum stable population size of a species that an ecosystem can support

What is an indicator species?

Species that show the type of environment it is e.g a high oxygen environment

What is competition?

When two or more individuals share any resource that is insufficient to satisfy their requirements

What is intraspecific competition?

Form or competition where members of the same species need the same resource in an ecosystem

What is the result of less resources for species?

Lower birth rates and/ or higher mortality rates

What is interspecific competition?

A form of competition where different species need the same resource in an ecosystem

What does the competitive exclusion principle state?

Two species that use the same resource in the same way in the same space at the same time cannot coexist

What is a fundamental niche?

A niche that you would expect it to be

What is realised niche?

The species’ actual niche, which varies due to competition

Why do ecologists collect data?

To allow comparisons between communities and species e.g the abundance of organisms and their pattern of distribution and if this is influenced by abiotic or biotic factors

How do ecologists get a representative sample?

• make sure sample size is large (40-50 quadrants)

What is a confounding variable?

An outside influence that changes the effect of a dependant and independent variable

When is a transect used?

Systematic sampling

• for collecting data on immobile animals/ vegetation

• Monitors how communities change along an environmental gradient

What are belt transects?

• they study a wide strip across the area to be studied

• Either used by placing quadrants continuously along a line (continuous belt transect)

• Or placing quadrants at intervals (interrupted belt transect)

What are lone transects?

• are quicker than belt transects

• Samples on a point

• Less informative than belt transect as it may miss many organisms

What are kite diagrams?

• they represent the abundance of organisms along the transect

• Larger width = larger abundance of organisms

What makes animal sampling difficult?

Fast moving organisms can escape, hide or move when approached, making them hard to find and identify

What are some examples of different approaches to battle this difficulty?

1. Sweep netting → involves collecting invertebrates using fine mesh netting

   • make sure same size net is used

   • Some species may escape and you have to euthanise captured species

2. Kick sampling → collecting fish using nets

   • sweep the net for the same amount of time each time

   • Doesn’t catch much fish as they swim away fast

3. Trapping → collects larger more mobile animals in terrestrial environments

   • Doesn’t give reliable data as it changes the environment and therefore the animals behaviour

   • Animals have to be euthanised to prevent predators killing insects

What is the mark-release- recapture method?

Animals are caught, marked and released back into the community and then recaptured later to find the estimated population

How is estimated population calculated?

(1st unmarked sample size x 2nd marked sample size) / number of marked animals recaptured in 2nd sample

What assumptions are relied on for this technique of sampling?

• population doesn’t have immigration or emigration

• Very few or no deaths and births between sampling

• Non toxic, and non noticeable marking to predators

What is successsion?

The process of sequential change in community type overtime due to abiotic and biotic factors

What is the first stage of succession?

• pioneer community

• Pioneer plants (e.g lichen and moss) colonise the area first as they are tolerant to hostile conditions (e.g high salinity, large temp fluctuations)

What are lichens?

• species that grow on Pavements, walls and tree bark in urban areas

• Can tolerate high levels of pollution

• Shrubby lichens indicate clean air

• Flat lichens indicate pollution

What is marram grass?

• colonise sand dunes and are xerophytes (tolerant of dry and sandy conditions)

• Have thick outer cuticle and hairs to limit water loss

What do different pioneer species have in common?

• can rapidly multiply due to asexual reproduction

• Can photosynthesise in any light as long as there is some

• Are tolerant to extreme conditions meaning they have less competition from other species

As succession continues…

Species diversity of the community increases and the food web becomes more complex

What is the species diversity index?

The number of species present and the abundance of them

What is the two types of succession?

1. Primary succession of a previously unoccupied area e.g lichen, marram grass

2. Secondary succession In altered habitats where some organisms are already present e.g cleared forests

What are the stages of succession?

1. Pioneer community - few species , susceptible to change , few interactions to populations

2. Sub climax community

3. Climax community - many species , resistant to change , many interactions between populations

Describe the process of succession.

Succession is the sequential change in a community over time, taking hundreds of years. Different species can withstand the biotic and abiotic factors in the dynamic environment. Pioneer plants are the first to colonise the area as species like lichen and moss can withstand the hostile environments. This is now known as a pioneer community. Overtime, these species decompose and provide a more suitable environment for other species to live in as they are adapted to it. This results in more habitats and higher biodiversity of species in the area, leading to a climax community which is stable.

What are producers?

Autotrophs that convert energy so other organisms can use it by photosynthesis which adds biomass to the area

What is biomass?

All the organic material in the ecosystem available to organisms

How do you measure biomass?

1. dessicate the organism and weigh their dry biomass

2. Use population estimates to scale up the biomass to the whole system

3. Units are gm^-2 when an area is being samples and gm^-3 when a volume is being sampled

How do you dry an organism?

• open it up

• Put in desiccating oven at around 100 degrees C

What does calorimetry calculate?

The amount of chemicals energy stored in an organisms dry biomass

What are the adaptations a calorimeter have to be more efficient?

• a stirrer to make sure water flows over the sample all the time

• Highly insulated so only the water is heated

What is primary productivity?

The rate at which plants convert inflight into chemical energy

• Unit is kJm^-2year^-1

What is gross primary productivity?

The check energy store in plant biomass in a given area in a given time

What is net primary productivity?

The chemical energy store that is left after the plant loses energy to respiration

How do you calculate net primary production?

Net Primary Production = Gross Primary Productivity - Energy Used or Lost

(NPP = GPP - R)

What are consumers?

Heterotrophs that must eat other organisms for nutrition

What are consumers grouped into and what are they?

• herbivores - eats producers

• Carnivores - eats consumers

• Omnivores - eats producers and consumers

• Detritivores - eats wastes and part of dead consumers and producers

How can the energy flow from organisms eating one another in an ecosystem be represented?

• ecological pyramids (tropic level diagrams or energy pyramids)

• Food chains

• Food webs

What is this type of ecological pyramid?

Trophic level diagrams

What type of ecological pyramids is this?

Energy pyramid

What do energy pyramids show?

How much energy is passed from one trophic level to the next (on average 10% energy transferred)

What is the difference between a food chain and a food web?

• food chains are single pathways of energy transfer and a simple

• Food webs are made of many interacting food chains and are more accurate as most organisms feed on and are eaten by more than one thing

How do you work out net production?

N = I - ( F + R )

I=chemical energy in ingested food

F= chemical energy lots in faeces and urine

R = energy lost through respiration

How do you work out percentage efficiency?

(Energy available after the transfer / energy available before the transfer) x 100

What does yield mean?

Amount of harvested material

What are the 4 main strategies used to improve efficiency of crop production?

• fertiliser to maximise growth

• Pesticides to minimise crop loss

• Fungicides to prevent fungal infections

• Herbicides to reduce competition from weed species

What are inorganic fertilisers?

• NPK is the most commonly used one

• Adds nitrate, phosphate and potassium ions in the soil to prevent limiting factor of not enough mineral ions available in soil

• Are very effective as they have immediate effect

• Are expensive

• Due to it being soluble the ions are quickly leached out of the soil and into lakes and rivers causing environmental damage

What are organic fertilisers?

• Animal manure and composted vegetable matter are examples of

• They still contain NPK but in organic compounds such as urea and cellulose

• These are digested by the soil organisms which release inorganic ions that the plants can take up in their roots

• This causes less harm to environment

What are pesticides?

• kill or reduce the population of organisms damaging crops by slowing growth or preventing reproduction

• Pesticides must have no effect on the crop but effective against the pest

• Multiple different chemicals can be used on the same plant

• However use of pesticides can cause persistence (remains toxic for long time) and bio accumulation (doses of pesticides transferred to predator organism when they eat their pray, stored in fatty tissues)

What are herbicides?

• kill off competing plant species

• Broad spectrum herbicides kill of ALL plant species and can only be used PRIOR to sowing the crop plant

• Selective herbicides affect CERTAIN types of plants only and can be applied WHILST the crop grows

How can simplifying the food chain increase the efficiency of animal production?

• only consuming primary consumers minimised the energy lost to surrounding due to fewer trophic levels between producers and top consumer (humans)

How can reducing the energy lost through respiration increase the efficiency of animal production?

• keeping animals in pens restricts movement.

• Indoor pens means less energy is used to maintain body temperature

• This means a greater proportion of the energy consumed in food is transferred into biomass and less is lost as heat energy to the surroundings (REMEMBER)

How can reducing other losses increase the efficiency of animal production?

• giving animals more digestible freed reduces energy lost in faeces

• This means a greater proportion of the energy in the food is used to ass biomass and less in faeces

What is nutrient cycling?

The cycle of simple organic molecules transferred into complex organic molecules

How are nutrients cycled?

• nutrient taken up by producer which transfers it into a complex organic molecule (e.g amino acid, protein)

• Elements from the nutrients pass into the consumers

• Complex molecules hydrolysed when producers and consumers die, releasing simple inorganic molecules (e.g CO2 , N2 , H2O)

What are the two groups of decomposers?

• detritivores (e.g worms)

• Saprobiotic organisms (e.g bacteria)

What are detritivores?

• Animals that digest lots of the solid materials but can’t digest cellulose or lignin

• They increase the SA:VOL ratio of dead matter, making decomposition more efficient

What are saprobiotic organisms?

They use extra cellular digestion to carry out decomposing by breaking down cellulose/ lignin into soluble nutrients that they can absorb

• they release co2 and h2o as a product of this

How can detritivores have a positive effect on saprobiotic organisms?

Worms burrowing in the soil maintains anaerobic conditions for the saprobiotics

What are mycorrhizae?

fungi that are long thing strands called hyphae connected to plant roots to increase their surface area so the plants can absorb scarce ions from soil

What is nitrogen fixation?

Nitrogen fixing bacteria that live in the nodules in the roots of some plants that reduces nitrogen gas to ammonia

What is nitrification?

Nitrifying bacteria that oxidises ammonia into nitrite ions then into nitrate ions

What is denitrification?

Anaerobic denitrifying bacteria that converts nitrate into nitrogen gas and nitrogen oxides that is then lost to the air, meaning they are inaccessible to plants

• commonly associated with flooded ground where all aerobic processes stop

• This can be tackled by adding drainage

What is ammonification?

Microbial saprophytes that break down proteins in dead material to form ammonia by digesting proteins into amino acids using protease and then removing the amino groups from the amino acids using deaminase

Why is phosphorous important for plants and animals?

Because it is used to make biological molecules such as DNA, ATP and phospholipids

Where is phosphate found?

• In rocks

• Dissolved in oceans in the form of phosphate ions

What are the 8 steps involved in the phosphorous cycle?

1. Phosphate ions released from rocks by weathering

2. Phosphate ions taking into plants via the roots → hyphae increases the rate of this as it makes the roots SA larger

3. Phosphate passed through food chains as organisms containing phosphate are eaten

4. Phosphate ions lost in faeces and urine

5. Saprobiotic organisms hydrolyse organic compounds in dead plants and animals, releasing phosphate into soil

6. Weathering of rock released phosphates into aquatic environments

7. Primary producers containing phosphate are eaten, passing phosphate through aquatic food chains

8. Phosphate ions lost to soils through Guano (accumulated bird faeces)