8.4- Ecosystems

Question 1

What is an ecosystem

Answer 1

the interactions between species and their environment

Question 2

What does it mean when ecosystems are open systems?

Answer 2

both energy and matter can enter and exit

Question 3

How does energy enter and exit an ecosystem

Answer 3

enters as sunlight or stored in the tissues of organisms

lost in uneaten parts of organisms or through heat

Question 4

How does matter enter and exit an ecosystem

Answer 4

enters when an organism arrives

exits when an organism leaves

Question 5

Can matter enter and exit a closed system

Answer 5

no

Question 6

What is needed for stable ecosystems

Answer 6

1. recycling of nutrients
2. abiotic conditions
3. genetic diversity
4. energy supply

Question 7

1. recycling of nutrients

Answer 7

• recycling of nutrients allows the ecosystem to be self supporting.

providing chemical elements required for biosynthesis

Question 8

2. abiotic conditions

Answer 8

climatic variables such as temperature and rainfall has to remain within tolerance zones to prevent migration or extinction

Question 9

3. genetic diversity

Answer 9

high levels of genetic diversity provides the capacity for adaptation to changes in the environment

Question 10

4. energy supply

Answer 10

constant energy supply is required for metabolic processes

Question 11

What are mesocosms?

Answer 11

enclosed environments that allow for the observation of a small part of the natural environment

Question 12

Terrestrial mesocosm required materials

Answer 12

slow growing plants
- function as producers

pre-moistened soil
- provide nutrient supply

sphagnum moss
- seperates soil layers

charcoal
- aerates and prevents mould
drainage material

Question 13

Aquatic mesocosm material requirements

Answer 13

small organisms
- low numbers of primary consumers

small aquatic plants
- producers and oxygenate water

clear water
- allow light to penetrate

base layer
- organic substrate to provide nutrients

Question 14

What is a keystone species

Answer 14

species with a disproportionately large impact on the environment relative to its abundance

Question 15

What are the three ways keystone species may influence communities?

Answer 15

Predators
- exert pressure on lower trophic levels to prevent monopolisation of resources
Mutualism
- support life cycle of species
Engineers
- rebuild environment that promotes species survival

Question 16

Terrestrial plant- Black cherry

sustainability of resource harvesting

Answer 16

• hardwood tree in North America
• used for furniture production
• slow growing therefore requires sustainable harvesting
  1. selective felling: picking specific trees to harvest to create gaps in the forest canopy promoting new growth. This leaves behind enough plants to ensure seedling growth
  2. requires monitoring to ensure sustainability

Question 17

Marine animal- Alaska pollock

sustainability of resource harvesting

Answer 17

• fish species in the North Pacific
• rapid growth, requires sustainable harvesting to manage population levels
  1. nets: that do not damage ocean floor
  2. bycatch must be below 1%

Question 18

Sustainability of Agriculture

Answer 18

SCALE
- supply of fertilisers
- carbon footprint
- agrochemical pollution
- leeching of nutrients
- erosion of soil

Question 19

SCALE
- supply of fertilisers

Answer 19

• chemical fertilisers are expensive and alter soil composition
• organic fertilisers reduce harm and difficulties associated with chemical fertilisers

Question 20

• carbon footprint

Answer 20

• land clearing, fertiliser production and transportation of products increase Co2 emissions
• renewable energy sources reduce impact of food production on Co2 emissions

Question 21

• agrochemical pollution

Answer 21

• herbicides, pesticides etc improve yield but harm native species
• GMO can create crops that are inherently resistant to pests and diseases

Question 22

• leaching of nutrients

Answer 22

• rainfall can wash fertilisers into bodies of water causing eutrophication
• leaching can be minimised by timing use to rainfall periods and using smaller amounts

Question 23

• erosion of soil

Answer 23

• land needs to be cleared for agriculture, removal of trees makes soil less stable and more likely to erode
• farmers can plant cover crops to hold topsoil together

Question 24

What is rewilding

Answer 24

use of conservation strategies to restore ecosystems to natural conditions

Question 25

Rewilding strategies

Answer 25

1. species reintroduction 2. habitat connectivity 3. reducing human influence

Question 26

Species reintroduction

Answer 26

reintroduction of keystone species and apex predators to control consumer populations to promote biodiversity of vegetation

Question 27

Habitat connectivity

Answer 27

establishment of wildlife corridors improves access to more resources

Question 29

Human influence

Answer 29

human activity and influence minimised by legislating wildlife zones to prevent activities such as fishing, deforestation etc.

Question 30

# NAMED EXAMPLE HINEWAI RESERVE IN NZ

Answer 30

- rewilding example - used to be farmland, now privately owned nature reserve - human influence to remove non-native species then human influence removed