Biology summary notes.

Module 4 –

Organisation within ecosystems – The biosphere is the part of the earth that contains living things. Biotic means living things. Biotic factors include the plants and animals that an

organism interacts with. Abiotic means non-living things. Abiotic factors include physical and chemical factors

in the environment. An ecosystem consists of the interaction of living things with each other and with their

non-living environment. An ecosystem is made up of many different species living together in the same environment.

The environment is all the abiotic factors that affect an ecosystem. Abiotic factors are unevenly distributed through an ecosystem. Ecology is the study of interrelationships of organisms with each other and the

environment. This determines their distribution and abundance. Distribution refers to the region where an organism is found. Abundance refers to the number of organisms in an area.

Impacts of abiotic factors in an ecosystem – Abiotic factors aren’t always distributed evenly throughout an ecosystem. Producers are plants that make their own food through photosynthesis (autotrophs).

11.1a Check your understanding – 1. Distinguish between an ecosystem and an environment.An ecosystem consists of the interaction of living things with each other and with their non-living environment, whereas an environment is all the abiotic factors that affect an ecosystem.2. Define the term ‘abiotic factor’.Abiotic factors are the non-living factors of an environment. These include the temperature, water availability, sunlight availability and many more.3. List the abiotic factors that can affect a species in a terrestrial environment.Temperature, sunlight availability, water availability, soil nutrient levels, wind levels, etc.4. Describe one terrestrial and one aquatic ecosystem in terms of the abiotic factors that

are present.Terrestrial – water availability, temperature, sunlight availability, soil nutrients.

Aquatic – temperature, water salinity, pH levels of the water, sunlight availability, water pressure.5. In your own words, explain why an abiotic factor such as light or nutrient availability

would affect the types of organisms that are present in an ecosystem. Use a specific example.

Organisms that need a specific abiotic factor, such as light or nutrient availability, to live would be drawn towards ecosystems that occupy a large amount of that abiotic factor. For example, fish are found in water because water is essential for their life.6. Why is it important to gather information on an organism’s abundance and

distribution?It’s important to gather information on an organism’s abundance and distribution in order to find out what specific factors that organism needs to live. You can also use abundance and distribution to learn about how an organism’s body functions and how they live.7. Are abiotic factors always evenly distributed throughout ecosystems? Give an example.Abiotic factors are not always evenly distributed throughout ecosystems. An example is sunlight and the ocean. In shallow water, sunlight is plentiful and plants use this sunlight in the process of photosynthesis. However, deeper water doesn’t have a lot of sunlight, therefore plants cannot produce food. Also, the deeper you go into the ocean, the colder it gets due to the lack of sunlight.

Impacts of biotic factors in an ecosystem – Living organisms can affect each other directly by symbiosis and predation or

indirectly by competing for resources. The simplest community interactions are: predation, competition and symbiosis

(mutualism, commensalism and parasitism). Predation is where an organism (the predator) kills and eats another organism (the

prey). Competition is when two or more organisms use one or more resources in common.

Species can compete directly/indirectly. Animals compete with each other for resources, food and shelter.

Intraspecific competition is when organisms of the same species are competing with each other.

Interspecific competition is when organisms of different species are competing with each other.

Allelopathy is the production of biomolecules by one plant, that can positively/negatively affect another plant.

Symbiosis is the interaction between two different organisms living in close physical association.

Mutualism is an interspecific interaction where both species benefit from the relationship.

Commensalism is an interspecific interaction where one species benefits and the other isn’t harmed/benefitted.

Parasitism is an interspecific interaction where one species benefits and the other is harmed.

Host refers to an organism that harbours a parasite.

11.1b Check your understanding – 1) Distinguish between intraspecific and interspecific competition, using examples.

Intraspecific competition is competition between 2 organisms of the same species. E.g. 2 male beetles competing for a female beetle. Interspecific competition is when 2 organisms from different species compete. E.g. lion and tigers competing for a deer. 2) Briefly summarise the ways in which plants compete.Plants compete through allelopathy. They produce certain chemicals that help them kill other plants around them in different ways.3) Why do animals compete within an ecosystem? Identify a possible consequence of

competition between 2 species.Animals compete for resources such as food, water, shelter and mates. A possible consequence of competition is the death of organisms; during direct competition, an organism may get hurt/killed by the other.4) Define symbiosis. Define and give examples of the following symbiotic relationships:Symbiosis is the close relationship between 2 organisms where at least 1 of them is benefitted.

a. MutualismMutualism is a symbiotic relationship where both organisms are benefitted. Examples include clownfish and anemone.

b. CommensalismCommensalism is a symbiotic relationship where 1 organism is benefitted and the other isn’t benefitted/harmed. Examples include small ferns on tree trunks.

c. ParasitismParasitism is a symbiotic relationship where 1 organism benefits and the other is harmed. Examples include tapeworm inside a human.

Ecological niches occupied by species – The part of an ecosystem that an organism occupies is called a niche. A niche refers to

all the resources that a species uses, including biotic and abiotic factors. No two species can occupy the same niche. This is known as the competitive

exclusion principle. Because of competition not all species are able to live in their ideal or fundamental

niche. The fundamental niche is the one that an organism would occupy if there were no competitors, predators or parasites. Due to this, organisms usually occupy a realised niche.

Predicting consequences for populations in ecosystems – Predators affect the distribution and abundance of their prey. This is a natural means

of population control. When there are a large number of prey available, the population of the predators

increases. As prey are consumed, their numbers decrease which will lead to a decrease in predators.

Several factors influence the predator and prey populations: number of predators, availability of prey’s food, reproduction rate, death rate, ratio of males to females, etc.

Competition between species for resources affects reproduction and survival rates. If there’s a lot of food, both species will increase in size, if there is a decrease in food,

there will be a decrease in the two species. When 2 species compete, the short-term effect is a decrease in population numbers of

one or both species. However, this could possibly lead to extinction. Symbiosis has the potential to contribute to: biodiversity, the development of new

species, and sources of new capabilities for organisms. Symbiosis causes an increase in biodiversity and therefore, more resilient ecosystems.

Disease is any process that negatively affects the normal functioning of tissues in an organism. This includes infectious and non-infectious diseases.

A pathogen is a disease-causing organism such as a bacterium or virus. For a disease outcome to occur, a pathogen must be introduced into a population

through direct or indirect means. The effect of disease on an ecosystem is to alter the balance of the food webs. This

will have an effect on predators, preys and humans. Devil facial tumour disease (DFTD) is a clonally transmissible cancer which is highly

contagious. It spread throughout the wild Tasmanian Devil population and is transmitted through social interactions and when they bite each other during a fight.

When a devil is bitten, a large, ulcerated tumour forms around the mouth and eyes which affects the devil’s ability to see and eat.

In 2008, the Tasmanian Devil was listed as endangered. Scientists are looking for a cure. They’re putting the healthy devils in isolation so that they could reproduce and re-populate. There are also several reports of successful treatment of DFTD. A vaccine is also being worked on.

11.1c Check your understanding –1. Distinguish between the following pairs of terms:

a. Niche and habitatA niche refers to all biotic and abiotic resources that a species uses and a habitat is the natural home of an organism.

b. Fundamental niche and realised nicheFundamental niche is a species’ ideal niche if there were no predators, parasites or competition. A realised niche is the niche an organism occupies due to restrictions placed on them when they want a fundamental niche.

2. State the consequences of the following to populations:a. Predation

Predators affect the abundance and distribution of their prey. Predation can lead to extinction of one species if there are too many predators.

b. CompetitionCompetition affects survival and reproduction rates. Can lead to death/extinction of a species.

c. SymbiosisCan lead to biodiversity, a new species, and sources of new capabilities for organisms.

d. Disease Disease affects the balance of the food web and can harm organisms and humans.

A recent extinction event – Extinction is the death of all of one species.

Megafauna – Megafauna are extremely large animals, most of which are extinct today. During the Pleistocene epoch (1.6 million – 10000 years ago), Australia was home to

a group of giant animals called the Australian megafauna. The last ice was the only ice age where humans were present, the humans survived

but most of the megafauna was wiped out. There are several theories as to what led to the extinction of the megafauna. Theory 1: Changes in climate. The ice age dried out the continent, fires broke out. Theory 2: The arrival of humans. The aboriginal people used to hunt the megafauna. Theory 3: Level of nutrients. Very low nutrient levels in Australian soil. Fossil have been found of the coexistence of humans and megafauna.

Thylacine – The Tasmanian Tiger. Pushed to the brink of extinction by white settlers. Is a marsupial and is related to the Tasmanian devil. Unseen since 1936. Classified as extinct. Looked like a large, long dog, with stripes and a heavy stiff head and tail. When hunting, it relies of a good sense of smell and stamina. Breeding occurred during winter and spring. Thylacine was a carnivore. They once lived throughout Australia and New Guinea. Predation and competition from the dingo may have contributed to the thylacine’s

disappearance from mainland Australia and New Guinea. Hunting and habitat destruction, leading to population fragmentation, are believed to

be the main reasons of extinction. The remaining population was further. Weakened by disease.

Search for evidence of past ecosystems – The law of superposition states that in any sequence of rocks that is undisturbed, the

oldest layers will be at the bottom and the youngest at the top. The law of original horizontally states that all sedimentary strata a deposited

horizontally and only tilt/bend due to forces. The law of lateral continuity states that a stratum of rock will be continuous until

something disturbs it (eg, erosion). The law of cross-cutting relationships states that in any rock sequence, the layer that

crosses or intrudes another is the younger rock layer.

Catastrophism is the theory that changes in the earth's crust during geological history have resulted chiefly from sudden violent and unusual events.

Gradualism is the hypothesis that evolution proceeds chiefly by the accumulation of gradual changes.

Palaeontology is the study of fossils. Geology is the study of the history of the earth through rocks.

Aboriginal and Torres Strait islander histories and cultures – Ancient aboriginal artworks are evidence for scientists. The paintings show images of animals and things that are thought to have existed

back then. The artworks also portray evidence of past climate change and landscape change.

Geological evidence – Banded iron formations are geological formations of alternating bands of iron-rich

and iron-poor sediments. Fossils are remains of living organisms or evidence of their past existence. Often, how a fossil looks gives us information about the climate and environment at

the time. Fossils are generally found in sedimentary rocks. There are many ways to classify fossils: Mineralised remains such as moulds and casts. Organic remains. Impressions – the shape of the external organism recorded in sediment. Trace fossils – fossils of a footprint, trail, burrow, or other trace of an animal rather

than of the animal itself. Geological timescale is a scientific model that represents past natural events in order

and allows scientists to infer cause and effect. Geochemical remains are remnants of organic molecules or isotopic ratios only

associated with living things.Ice core drilling –

Climate refers to weather conditions prevailing in an area over long periods of time. Climate change is a change in regional or global climate patterns. Anthropogenic climate change refers to human impacts on the climate, causing it to

change. Scientists are interested in changing climates in the past as it will help them to predict

future events of current climate change.

Bubbles in ice help scientists understand the composition of the air at the time that the ice was formed.

Antarctic snow forms in layers, therefore, the deeper layers are older than the top ones.

Scientist drill down in ice to gain more insight on the past. Ice in places such as Antarctica holds information about the abiotic and biotic factors

of the ecosystems at the time the ice formed. As snow falls every year, gases and particles are trapped inside.

Scientists use drills to drill out ice cores to study their layers.Radiometric dating –

Radiometric dating is the process where scientists measure the age of objects or materials using the decay rates of radioactive components.

Techniques such as nuclear reactors, mass spectrometers, laser beams and special microscopes.

SHRIMP is a technique that has allowed scientists to identify the oldest rocks on Earth.

Fission track dating is a technique that is used to estimate the age of a mineral sample by observing uranium fission tracks.

Luminescence dating is another dating technique that measure the amount of radiation trapped in a mineral using heat or laser light. The longer the crystal has been buried, the brighter the luminescence.

Gas analysis – Scientists can use the data from ice cores to figure out the atmospheric concentrations

of certain gases. Scientists use ancient carbon dioxide levels to infer past climates.

Evolution of Australian biota – Scientists analyse evidence of organisms from the past to determine if present-day

organisms may have evolved from them. Fossils provide evidence of past organisms. The evolution of Australian mammals and plants is closely linked to the evolution of

the Australian climate and its tectonic setting as the continent drifts slowly north.Changing Australian ecosystems: abiotic and biotic changes over time –

If the climate in an ecosystem changes, so does the distribution and abundance of organisms in that ecosystem.

The abundance and distribution of present-day plants in Australia are from 3 origins:o Those already on the continent when it split from Gondwana.o Those that came from south-east Asia to Australia.o Introduced species.

The origins of animals that led to present-day fauna:o Original residents – before Gondwana.o Asian immigrants – arrived when sea level was low.o Introduced by immigrant traders or late arrival aboriginals – 4000 years ago

(DINGO).o Introduced by European immigrants – 200 years ago.

Changes in Australian ecosystem is linked to the movement of continents and the subsequent effects on climate.

Sclerophyll plants –o Adapted to dry climates.

o Have thin, small leaves with a very thick waxy cuticle, which makes them very resistant to drying out.

o Australian flora is dominated by 3 main sclerophyll plants: eucalypt (gum trees), banksia (bottle brush), acacia (wattle).

Human-induced changes leading to extinction –o Extinction is a normal and natural part of the evolution of life on earth.o There have been 5 mass extinction events in earth’s past. Causes included: volcanic

activity, asteroid impact, changes in climate, sea levels and atmospheric and oceanic chemistry.

o Anthropogenic pressures are caused by human activity and restrict the range of other species whose population numbers and genetic variation may eventually become so low that some species may become extinct.

o Causes of extinction: habitat destruction, invasive species, pollution, overexploitation, and climate change.

Habitat destruction –o Occur when humans alter/remove an environment.o Main reason why this happens to support the human populations.o Natural habitats are changed or destroyed to harvest resources so that humans have

shelter, water, food and resources.