Biology - Chapter 4: Ecology

ecology

the study of the interactions/relationships between living organisms and their environment

biosphere

part of the planet that containing living organisms, i.e. where life can exist.

it’s composed of the lithsphere,atmosphere and the hydrosphere

ecosystem

a group of clearly distinguished organisms that interact with the non-living, physical environment as a unit

i.e.

ecosystem = community + environment

habitat

the physical place where a plant or animal lives

abiotic factors

non-living factors

e.g. shade, currents, altitude, temperature, light intensity

example: daisies like a high light intensity area so they grow in open, out of shade areas

biotic factors

living factors

e.g. presence of predators, parasitism, competitors, food availability

climatic factors

the average weather conditions over a long period of time

e.g. rainfall, salinity (salt conc.), wind, temperature

edaphic factors

factors related to the soil that affect organisms in an ecosystem

e.g. minerals in the soil/soil type/mineral content, temperature of the soil

energy flow

• Energy flow is the movement of energy, starting with the sun, and passing from one organism to another.

• As energy flows from one organism to the next, 90 % of it is lost in the form of heat due to metabolism, only a small amount of energy is passed to the next organism

• This limits the length of a food chain.

producers

organisms capable of making their own food by photosynthesis and other means, e.g. green plants

primary producers

the first members of a food chain, usually green plants

consumers

organisms that take in food from another organism/feed on other organisms. they cannot make their own food

primary consumers

feed on producers

e.g. herbivores, decomposers, detritus feeders

secondary consumers

feed on primary consumers

e.g. carnivores

tertiary consumers

feed on secondary consumers

e.g. humans

food chain

a sequence of organisms in which each one is eaten by the next member in the chain

shows how energy stored in food passes from organism to organism during feeding

food web

consists of two or more intersecting/interlinked food chains

trophic level

feeding position of an organism in a food chain

i.e. primary consumer, then secondary consumer and so on

pyramid of numbers

shows number of individuals at each trophic level of a food chain

niche

the functional role an organism plays in the community/ecosystem

* no two species can occupy the same niche in the same environment as they will be competing for resources

decomposers

play an important role in breaking down dead organic matter and returning nutrients to the soil

e.g. bacteria and fungi

detritus food chain

one where the chain begins with dead organic matter & animal waste

matter

this is recycled over and over again, primarily in the CO2 cycle

nutrient recycling

the ways in which the elements (e.g. N and C) are exchanged between the living and non-living components of an ecosystem

i.e. nutrients are recycled so that they can be reused

Carbon and Nitrogen found in plants and animals are continuously recycled and reused in the environment. Decomposers such as bacteria, and fungi break down the remains of dead plants and animals and release the nutrients back into the environment.

pollution

the addition of any unwanted or harmful substance to the environment by humans

human impact on an ecosystem - agricultural pollutant

eutrophication

pollutant: slurry → liquified waste materials produced by animals and is used as fertiliser

effects:

1. slurry enter rivers or lakes during heavy rainfall with causes algae to grow (algal bloom)

2. when algae die and decompose, oxygen is absorbed and therefore the oxygen levels in water falls

3. water plants and animals die due to lack of oxygen

eutrophication: the addition of nutrients to fresh water

control/conservation: slurry should be stored in leakproof pits & animal waste should be spread on dry land

conservation

the management of our environment which will prevent the death and extinction of organisms in future generations

conservation in fisheries

Problem → small mesh size of fishing nets catch immature fish before they can spawn, hence fish population declines & overfishing, reducing the number in fish stocks

Conservation practice → use fishing nets with larger mesh size so smaller fish will escape & using fish quotas to ensure only certain amount of fish will be caught

Waste management in fisheries:

• problem: disposing fish heads, skin and bones produced during fish processing…very alkaline

• waste management: dry and pulp waste used as pig feed → treated with formic acid to neutralise it

use of microorganisms in waste management and pollution control

biologically treats sewage to break down most organic matter

species

organisms that can interbreed to produce fertile offspring

population

all the organisms of the same species living in an area

it is controlled through…

• predation, parasitism, competition & symbiosis

community

all different populations of organisms living in an ecosystem

flora vs fauna

flora = plants

fauna = animals

aquatic environmental factors

• light penetration:

  plankton grow best in the upper layers of water due to higher light intensity

• current:

  currents move organisms. Plants and animals are washed away. There may be a need for attachment (e.g. limpets & many seaweeds)

competition

occurs when organisms struggle & fight for a resource that’s in short supply

Two types of competition:

contest & scramble competition

• contest competition - the physical struggle and fight between two organisms & only one benefits (gets the resource)

• scramble competition - all competitors get some of the resource but none get enough to survive

types of competition between species

• intraspecific competition - takes place between the same species

• interspecific competition - takes place between different species

autotroph

organism that can make its own food

heterotroph

organisms that cannot make their own food & obtains its food via a different source

parasitism

occurs when one organism (the parasite) obtains its food from a live host (the second organism), causing harm and disadvantage

types:

exoparasites/ectoparasite - live on outside of host

endoparasites - live inside host

parasite

a living species that obtains its food from another different living species (the host) and usually causes harm to the host.

saphrophryte

an organism that obtains its food from dead or decaying matter

herbivore

feeds on plants only

omnivore

feeds on plants and animals

carnivore

feeds on meat only

detritus feeders

feed on small parts of dead and decomposing animals and plants, they begin the process of decomposition

e.g. Earthworms, and wood lice are detritus feeders

pyramid of numbers

represents the number of organisms at each trophic/feeding level in a food chain

limits of the pyramid of numbers

• don’t take into account the size of the organism

• parasitic food chains often give rise to an inverted pyramid of numbers

• numbers of organisms can be so great that the pyramid cannot be drawn to scale

adaptation

• adaptation is a feature or a behaviour of a plant or animal which helps it survive

• adaptations can be structural or behavioural

examples of adaptation

• ladybird:

  • Strong mouth parts to chew aphids

  • Bright colour deters predators

  • Hibernates to avoid food shortages and cold weather

• bat:

  • Have fur

  • Webbed limbs

  • Nocturnal

  • Echolocation

the carbon cycle

1. Role of primary producers (photosynthesis and cellular respiration in plants)

   Carbon present in the air as carbon dioxide is absorbed by plants (primary producers). Via photosynthesis, they produce food in the form of carbohydrates.

   Respiration by plants return carbon dioxide to the atmosphere once again.

2. Role of primary consumers (carbon fixation and cellular respiration in animals)

   Herbivores obtain their food via plants, & carbon gets accumulated and fixed into their bodies in the form of organic carbon, a process known as carbon fixation.

   Respiration by animals release carbon dioxide back to the atmosphere.

3. Role of Detritus Feeders (Decomposition)

   Once plants and animals die, the fixed organic carbon is released back into the atmosphere as carbon dioxide gas through decomposition by the detritus feeders

4. Role of Fossils and Fossil Fuels (Combustion)

   The carbon that is leftover in the body of the dead organisms after decay becomes fossil fuels over many years, which on combustion releases the carbon stored in them back to the atmosphere thus completing the cycle

5. Role of microorganisms

   return carbon to the atmosphere by decomposing dead organic matter

importance of the carbon cycle

To maintain the balance of carbon in nature. Since atmospheric carbon dioxide determines the rate of photosynthesis by the producers, which acts as the primary source of food production on earth, the carbon cycle helps to sustain life on earth.

global warming

1. Levels of CO2 in the environment have risen in recent years.

2. This is due to deforestation, and burning of fossil fuels.

3. CO2 is a greenhouse gas because it allows heat from sun pass through earth’s atmosphere, but won’t let this heat escape.

4. Increased levels of CO2 have caused a rise in world temperatures.

rising temperatures result in…

• glaciers melting: causes sea levels to rise, therefore coastal cities may be at risk of flooding

• ecosystems will change: some species will move farther north, others wont be able to move and could become extinct

• weather patterns will change; hurricanes and other storms will be likely to get stronger

• the gulf stream could change direction, hence Irish weather is affected

the nitrogen cycle

all organisms need nitrogen to make protein, DNA and RNA

stages of the nitrogen cycle

1. Nitrogen fixation: through nitrogen fixing bacteria, they change nitrogen gas into nitrates/ammonia which is a form that plants can use. Lightning is also a separate process in which causes a little nitrate to fall in the rain

2. Absorption: plants absorb our nitrate, and some animals also consume plants, transferring the nitrogen

3. Decomposition: this is the breakdown of dead, organic matter by bacteria and fungi, in order to recycle nutrients and return them back to nature (animals also excrete urea through urination)

4. Nitrification: due to ammonia being released as a result, nitrifying bacteria convert ammonia into nitrites, then intro nitrites

5. Denitrification: denitrification then occurs when denitrifying bacteria convert nitrates back into nitrogen gas

benefits of conservation

• prevents extinction of organisms

• maintains biodiversity

• some organisms may have uses in the future

waste management

1. waste may contain disease-causing microorganisms

2. toxic chemicals may leak from waste into drinking water supplies

3. nutrients released from waste slurry may cause eutrophication

4. waste in landfill sites is unsightly and smelly, potentially attracting rodents

5. incinerators burn waste at high temperatures. Poisonous gases may be released in the process

advantages and disadvantages of incineration

advantages:

• very little waste produced

• less reliance on landfill sites

• energy produced can be reused

disadvantages:

• produce carbon dioxide

role of microorganisms in waste management

1. bacteria break down sewage in sewage treatment plants

2. bacteria can be used to break down oil spillages at sea

3. bacteria can be used to break down harmful chemicals in the soil

4. bacteria and fungi are used in the process of decomposing