C.3 Impacts of humans on ecosystems

Question 1

What are the two ways to describe species within any ecosystem?

Answer 1

Endemic or alien species

Question 2

What is an endemic species?

Answer 2

Those which are native to a defined geographic region

Question 3

What are alien species?

Answer 3

Those that have been transferred from their natural habitat to a new environment

Question 4

When is a species classed as invasive?

Answer 4

If an introduced alien species should have a detrimental effect on pre existing food chains

Question 5

What does the competitive exclusion principle state?

Answer 5

That two species cannot occupy identical niches within a community

Question 6

What is the argument to support the competitive exclusion principle?

Answer 6

One species will have a competitive advantage and survive at the expense of the other

Question 7

What happens to minimise direct competition between species in nature?

Answer 7

Evolution via natural selection causing adaptations

Question 8

What are four advantages that invasive species possess?

Answer 8

• They have a larger fundamental niche
• Faster reproductive rates
• Lack a predator capable of limiting their survival
• Have certain features suited to the new environment

Question 9

Why were cane toads introduced?

Answer 9

To control the spread of the sugar cane beetle that was damaging crops

Question 10

Why did the cane toad fail at limiting the beetle population?

Answer 10

It couldn’t reach the top of the sugar cane where the beetles live

Question 11

What is the cane toad classified as?

Answer 11

An invasive species

Question 12

What three reasons are the cane toads invasive?

Answer 12

• has a wide diet and depleted the prey population for native insectivores
• secretes a toxic chemical from its skin which has poisoned native predators
• carried diseases which has transmitted to native species

Question 13

Why have cane toads reproduced so successfully?

Answer 13

They have no natural predators

Question 14

What three strategies have been implemented to control rabbit populations?

Answer 14

• rabbit proof fences
• hunting and poisoning and rabbit borne diseases
  -Destroying rabbit warrens

Question 15

What effect have the rabbits had on native australian ecology?

Answer 15

• killed native plant species by ringbarking
• loss of said plants have left topsoil exposed and vulnerable to extensive erosion

Question 16

Why were wild rabbits reproducing so quickly?

Answer 16

As australian conditions promoted a population explosion

Question 17

When and where were European rabbits introduced?

Answer 17

To australia with the arrival of the first fleet

Question 18

What are the three main methods of population control?

Answer 18

Physical
Chemical
Biological

Question 19

What is physical control?

Answer 19

The removal or restriction of invasive species by manual or mechanical measures

Question 20

What are examples of physical control?

Answer 20

Barriers, fences or removing habitats by trimming

Question 21

How else can population numbers be reduced physically?

Answer 21

Hunting, trapping and culling

Question 22

What is the problem with physical control methods?

Answer 22

Not species specific and can impede endemic wildlife

Question 23

What is chemical control?

Answer 23

The use of chemical agents to limit population numbers and spread

Question 24

What are examples of chemical control?

Answer 24

Herbicides, pesticides or other compounds

Question 25

What is the disadvantages of chemical control?

Answer 25

Can be detrimental to local wildlife, expensive and have moderate specificity

Question 26

When will the effect of chemical agents become more pronounced and why?

Answer 26

In higher trophic levels due to biomagnification

Question 27

What is biological control?

Answer 27

Using a living organism to control an invasive species

Question 28

What might the biological control do?

Answer 28

Eat the invasive species or cause it become diseased

Question 29

Why must biological agents be assessed before release?

Answer 29

To ensure they do not become invasive themselves

Question 30

What are examples of biological control?

Answer 30

Vedalia beetle and myxoma virus

Question 31

Why must biological control agents be monitored?

Answer 31

For unintended side effects

Question 32

What is the cottony cushion scale?

Answer 32

A pest form australia that was released in california

Question 33

What did the cottony cushion scale do?

Answer 33

Damaged the californian citrus industry

Question 34

What is the vedalia beetle?

Answer 34

A predator from australia that was used in california as a biological control

Question 35

What did the vedalia beetle succeed in doing?

Answer 35

Limiting the numbers of the cottony cushion scale and minimise impact to the citrus industry

Question 36

What is biomagnification?

Answer 36

The process where chemical substances become more concentrated at each trophic level

Question 37

What is bioaccumulation?

Answer 37

The build of a chemical substance in the tissues of a single organism

Question 38

Why does biomagnification occur?

Answer 38

Because organisms at higher trophic levels must eat more biomass to meet their needs

Question 39

Why will higher order consumers experience increased contamination from a chemical substance?

Answer 39

As there energy transformations are only 10% efficient so they have to eat more to meet energy demands

Question 40

What is an example of a chemical substance which is biomagnifies?

Answer 40

DDT

Question 41

What is DDT?

Answer 41

A chemical pesticide that is sprayed on crops and subsequently washed into waterways at low concentrations

Question 42

What is the chemical description of DDT?

Answer 42

It is fat soluble and selectively retained in the tissues of an organism rather than being excreted

Question 43

What happens when DDT is sprayed on water to eliminate mosquito larvae?

Answer 43

It is taken up by the algae and passed on to primary consumers

Question 44

What happens at each subsequent trophic level to the concentration of DDT stored?

Answer 44

It increases due to increased food intake

Question 45

How did DDT affect fish?

Answer 45

It interfered with eggshell formation

Question 46

How did DDT affect birds?

Answer 46

Decreased survival rates of babies due to thinner shells

Question 47

When and why was DDT used as a chemical pesticide?

Answer 47

In the 1940s/50s to control insect borne diseases

Question 48

What did the use of DDT as an agricultural insecticide lead to?

Answer 48

The complete eradication of malaria in rich countries

Question 49

Why was using DDT in poor countries not as successful?

Answer 49

Eradication programs could not be sustained

Question 50

Why were eradication programs using DDT stopped?

Answer 50

Over safety and environment concerns

Question 51

What do they use for current interventions for malaria now?

Answer 51

Non spraying strategies like bed nets

Question 52

What are the four arguments supporting DDT spraying?

Answer 52

- It is affordable and effective - Once it stopped malaria rates and deaths increased -When sprayed health costs associated with malaria decreased - alternative strategies are not as cost effective or successful

Question 53

What are the three arguments against DDT spraying?

Answer 53

- associated with adverse health effects in humans - Persists in the environment for a long time - Is biomagnified in higher order consumers which is bad for ecosystems

Question 54

What are plastics?

Answer 54

A type of synthetic polymer found in clothes, bottles, bags and containers

Question 55

Why do plastics persist in the environment for centuries?

Answer 55

As most plastics are not biodegradable

Question 56

What is a macroplastic?

Answer 56

Large visible plastic debris (> 1mm)

Question 57

What is a microplastic?

Answer 57

Small plastic debris (<1mm)

Question 58

How can macroplastics be degraded into microplastics?

Answer 58

UV radiation and the action of waves

Question 59

Where will ocean currents concentrate plastic debris?

Answer 59

In gyres

Question 60

What are gyres?

Answer 60

Large oceanic convergence zones

Question 61

What does plastic debris do to the water?

Answer 61

Leach chemicals into it

Question 62

What does plastic debris absorb?

Answer 62

Toxic contaminants called persistent organic pollutants

Question 63

What absorbs more persistent organic pollutants and why?

Answer 63

Microplastics due to their smaller size and larger surface area

Question 64

How does plastics damage marine animals when they eat them?

Answer 64

- causes bioaccumulation and biomagnification of persistent organic pollutants - damages their stomach and cause them to stop eating

Question 65

Where are the laysan albatross nests found?

Answer 65

In the north pacific gyre where large amounts of plastic debris is found

Question 66

How does the albatross ingest large quantities of plastic?

Answer 66

As they feed by skimming the ocean surface with their beak

Question 67

Why is the mortality rate of albatross chicks high?

Answer 67

As adults can regurgitate the plastics swallowed but the plants can't

Question 68

Why do turtles eat a lot of plastic bags?

Answer 68

They mistake them for jellyfish

Question 69

How can plastic damage a turtle if ingested?

Answer 69

Plastic can be lodged in the oesophagus and cause future feeding problems

Question 70

How can plastic damage a turtle if it wraps around it?

Answer 70

Restricts movement and developmental growth