A Local Ecosystem 2

Question 0

Describe the relationship between prey and predator populations.

Answer 0

• predator populations will always be lower than prey populations
• predator population trends follow that of its prey e.g. if the prey numbers peak, the predator numbers will follow with a peak as well
• predators directly affect the population of their prey

Question 1

What are factors that affect the population of predators and prey?

Answer 1

• number of predators competing for prey
• availability of prey’s food
• birth rate (depending on age maturity and number of reproductive episodes per lifetime)
• death rate
• number of males and females
• size of ecosystem supporting prey and predators
• movement between ecosystems
• amount of shelter available

Question 2

Define: detrimental interactions

Answer 2

When one or more organisms are harmed or disadvantaged in a relationship.

Question 3

Define: beneficial interaction.

Answer 3

When one or more organisms benefit from a relationship.

Question 4

Define: predator to prey relationship.

Answer 4

This is a feeding relationship, where a predator (consumer) obtains its food by killing another organism (prey).

Question 5

Define: allelpathy.

Answer 5

Where a plant produces biochemicals to either harm or support other plants around it (usually harm). Allelopathy is usually used by a plant to clear its own space from other competitors. The more free space a plant has, the more nutrients, soil, water and sunlight it has available.

e.g. Eucalyptus litter and root exudates are allelopathic for specific soil microbes and plant species. Some pine trees are also allelopathic - their pine needles release acid into the ground when it falls from the tree.

Question 6

Define: symbiosis.

Answer 6

A term used for interactions in which two organisms live together in a close relationship that is beneficial to at least one of them.

Question 7

What are the types of symbiosis?

Answer 7

• parasitism - where one organism benefits, but the other is harmed. The parasite derives nutrients from a host. Usually not fatal. e.g. ticks and dogs.
• commensalism - where one organism helps the other but there is no benefit or harm in return e.g. small fish clean food scraps from larger fish.
• mutualism - where both organisms benefit. e.g. clownfish and anenome.

Question 8

Define: parasitism

Answer 8

Where a parasite obtains food and shelter from its host. Parasites can harm but are not necessarily fatal.
E.g. Ticks and dogs

Question 9

Define: mutualism

Answer 9

Where both species benefit.

E.g. Clown fish and anenome.

Question 10

Define: commensalism

Answer 10

Where one species benefits whilst the other is unaffected.

E.g. Barnacles and turtles and whales.

Question 11

What is the role of decomposers in an ecosystem?

Answer 11

• break down dead organisms into materials which can be recycled for use by other organisms.
• this returns nutrients to the soil.
• important for the nitrogen cycle.

Question 12

What are decomposers?

Answer 12

Fungi and bacteria.

Question 13

What are two ways nitrogen can get into the environment?

Answer 13

• when organisms excrete waste

- when organisms die. Nitrogen is converted to ammonia.

Question 14

What are two ways atmospheric nitrogen becomes part of living organisms?

Answer 14

• bacteria in the soil convert nitrogen in the air into nitrogen
• nitrogen combines with water during electrical storms to form acid rain
• • nitrogen fixation

Question 15

What is ammonification?

Answer 15

Where ammonia in the soil is converted into nitrates via bacteria.

Question 16

How is nitrogen returned to the atmosphere?

Answer 16

Nitrates are converted into gaseous nitrogen via denitrification.

Question 17

What is an autotroph?

Answer 17

A producer. These organisms can create their own energy - either by photosynthesis or chemosynthesis.

Question 18

What is a hetrotroph?

Answer 18

Consumers in a food chain. They are:

• primary consumers
• • herbivores
• secondary or tertiary consumers
• • carnivores
• • omnivores

Question 19

What is a primary consumer?

Answer 19

A herbivore.

Question 20

What is a secondary consumer/tertiary consumer?

Answer 20

Carnivores and omnivores.

Question 21

List the different tropic levels in order of what is eaten by what.

Answer 21

Producers are eaten by primary which are eaten by secondary consumers then tertiary consumers. Degraders - scavengers, detritivores and decomposers - feed on dead organisms and organic waste from different graphic levels.

Question 22

What is a tropic level?

Answer 22

A feeding level.

Question 23

What is a food chain?

Answer 23

Shows the flow of energy from one organism to another. A sequence of organisms whereby one is food for the next organism in the chain.

Question 24

What is a food web?

Answer 24

A complex series of food chains that connect to each other.

Question 25

What is a biomass pyramid?

Answer 25

Shows the amount of biomass through each level of the food chain.

Question 26

What happens to the amount of energy as you go up each level of the food chain?

Answer 26

90% of energy is lost per level. This is why, in a biomass pyramid, each higher level is only a tenth of the level below it.

Question 27

Define: biomass

Answer 27

The mass (weight) of living flesh in you.

Question 28

Define: adaptation

Answer 28

Any characteristic that increases an organism’s likelihood of survival and reproduction relative to organisms that lack the characteristic.

It is an inherited change at random.

Be careful not to assume that all characteristics of organisms are adaptations to their present day habitat and environment. E.g. Whales and dolphins have lungs.

Question 29

Describe a problem with identifying adaptations.

Answer 29

Some organisms still retain characteristics they have inherited from a long time ago when an organism once existed in a different habitat. An organism may still retain a characteristic or adaptation but it is now not of any use or related to its survival in its current habitat.
E.g. Whales and dolphins have lungs - characteristic of a land animal.

Question 30

List and explain the different type of adaptations.

Answer 30

• Structural: a physical characteristic e.g. A giraffe’s long neck, or an elephant’s trunk.
• Physiological: an organism’s function or process e.g. Desert hopping mic can produce highly concentrated urine to reserve water, sheep have four stomachs.
• Behavioural: the way in which an organism acts e.g. Seeking shade or being nocturnal.

Question 31

Identify and describe some adaptations of the kangaroo.

Answer 31

• digs a hole in the ground to rest in cooler grounds during hot days
• cools down itself by licking itself and bringing its tail underneath it
• crouched form reduces exposed surface area to the sun
• hops to conserve energy and keep a fast pace
• lightly coloured to reflect heat
• pouches are used to carry young
• able to suspend or pause embryo growth and shut down reproduction; this is suitable for times where little resources are available
• long ears assists in detecting predators from a long distance
• hind legs refill lungs with each hop, reserving energy
• can live on very little water
• come out at dusk and dawn

Question 32

Identify and describe some adaptations of the Eucalyptus tree.

Answer 32

• leaves are covered in a waxy oil. This prevents excessive water loss and reduces possible herbivores (only koalas can eat these). The oil is poisonous to other organisms
• leaves rotate with the sun’s direction, facing the thinnest side to it to reduce water loss
• allelopathic
• can photosynthesise through stem
• sunken stomata
• hard bark - reduces water loss
• have epicormic shoots; adapted to bush fires
• evergreen; but leaves can be shed to reserve water
• gum-like sap is produced to ward off predators
• rapid growth rate
• scleromorphic leaves - hard to touch
• can drop branches to attract water

Question 33

Describe some short term consequences of competition between species.

Answer 33

• decrease in population (one species will be significantly lower than the other)
• occupying a new niche or other environment factors e.g. A new food source or habitat

Question 34

Describe some long term consequences of competition between species.

Answer 34

• decreased population
• decreased population rates
• possible extinction or the loss of a species in an area

Question 35

Assess the human impacts on the Wonga Wetlands.

Answer 35

Cattle Farms 1830’s-20th century

• free range grazing; overgrazing and out competed natives like the eastern grey kangaroo.
• deforestation; rest area for birds; habitat and source of food, shelter and protection for many animals.
• Murray river’s banks began to weaken and erode away.
• farmers transferred the river bed’s rocks for building hard surface areas such as cattle yards
• increased turbidity; aquatic life health degraded; pollution; every organism that relied in the river negatively affected
• introduced species over competed native organisms for space and nutrients
• foreign grasses - benefitted cattle but only those.
• foxes preyed on small mammals, grounded birds and, most especially, turtles.

Hume Dam 1919

• altered the flooding and drying season from winter to summer
• many organisms’ reproduction cycles and migration relied on this cycle
• dried out excessively, especially aquatic life, even with regulated flooding

Albert City Council 2000

• treated water from Waterview Laboratory’s waste water treatment facility recovered the natural flooding and drying season
• waste water during summer is allocated to irrigating tree plantations, e.g. Red Gum
• waste water in winter (up to 20 mega litres in total)
• plantations have been planted to regenerate the lost vegetation. 160 000 small plants and 150-60 trees
• removal of cattle and constant supervision and extermination of foreign species
• Aquatic Environment and Education Centre has attracted tourists, universities and schools. This ultimately raises awareness of the fragility and need to preserve the wetlands to the public for future generations.

Question 36

Identify human impacts in the Australian ecosystem.

Answer 36

Introduced species

• rabbits, foxes, cane toads, lantana, Paterson’s curse, prickly pear, water hyacinth
• different adaptations outcompete native species

Land management

• land clearing
• reduces biodiversity and habitats - endemic species especially endangered
• soil erosion and land degradation
• salinity

Overharvesting/ hunting

• eventual reduction in soil nutrients and animal/plant stock
• crop rotations
• over harvesting of waterways
• extinction

Rabbits

• 24 to start with
• rapid reproduction
• outcompetes for food
• erosion from burrowing
• take up space
• viruses - mixamatosis - to control

Pollution

• harmful chemicals and trash
• water and air pollution - acid rain
• increased green house effect
• entanglement of animals with hazardous materials
• noise pollution, unknown responses and separation