Changing Ecosystems: Unit 3, Topic 2

Question 1

What is Succession? What are the two type sof succession?

Answer 1

the natural process by which ecosystems change and develop over time. Where one community is replaced by the next occurs after disturbance.

Primary and Secondary

Keywords:
Sere: the entire sequence of communities
Seral community: Intermediate stage of ecological succession advancing towards the climax community
Pioneer plant: a plant capable of invading care sites.

Question 2

Explain what Primary Succession is

Answer 2

The colonisation of plants in a barren place (no soil due to catastrophic events). he emergence of an entirely new ecosystem.
Nudation: the development of a bare site

1. pioneers colonise the area. Thin soil is made from secreted acids.
2. Thin soil layer allows for moss -> moss dies, giving nutrients to the soil.
3. Bacteria, fungi, and invertebrates form a simple community.
4. enough soil for grass, and fern -> when dead, more organic matter in added.
5. Deeper soil holders more water
   -> small shurbs colonise -> nutrients availability increases.
6. Trees establish -> development of the climax community on mature soil.

Question 3

Explain what secondary succession is.

Answer 3

• The recolonisation of disturbed plant communities - soil is already present.
• Destroyed by natural forces (fire, flood) OR human activities.
• Grows faster and will quickly reach a climax community.

Question 4

What are the differences of Primary and Secondary Succession?

Answer 4

Primary Succession:
- occurs in a land where there is no initial vegetation
- Surface soil covers is absent when primary succession starts
- Pioneer species come from outside environment
- need more time to complete

Secondary Succession:
- Occurs in land that has primary vegetation
- Occurs where soil cover is present
- Pioneer species develop partly from existing species
- Takes comparatively less time

Question 5

What are the similarities between Primary and Secondary Succession?

Answer 5

• Results in a climax community
• Shrubs and small trees grow
• Community of organism inhabiting an area is gradually changing

Question 6

What is a pioneer species? What are their traits?

Answer 6

Organisms (Typically plants) capable of establishing on bare environments - also referred to as opportunistic species.

Traits/features:
- tolerant of extreme conditions
- autotrophic
- small
- photosynthetic
fix nitrogen into the soil through their relationship with specialised bacteria.
- rapid seed germination/dispersal
- Rapid reproduction -> typically R-selected
- ability to grow in poor soils with low nutrients

Question 7

What is a fossil record?

Answer 7

• Fossilised remains of organisms
• Biotic changes can be tracked using fossil records through ice/soil cores.

Question 8

What is temporal and spatial change?

Answer 8

Temporal change - Change in time
Spatial change - change in space/place

Question 9

What is Urbanisation?

Answer 9

• reduces biodiversity
• causes rapid change in large magnitudes.
• changes the ecosystem for a long time, often permanent
• increase the output of gaseous and material wastes that are disposed into the atmosphere/land/water.
• caused by humans most of the time

Question 10

What is Habit Destruction?

Answer 10

• clearance of native vegetation poses threats to biodiversity.
• when native vegetation is cleared, habitats that were once continuous become fragmented (habitat fragmentation)

Question 11

What is land and soil degradation?

Answer 11

reduced vegetation = less organic matter being returned to the soil -> causes nutrients depletion and increasing erosion

Question 12

Explain what salinity is

Answer 12

When natural vegetation is replaced with crops (require irrigation) = salinity
irrigation increases groundwater -> raises the water table and its often-high salt content to the surface -> causes water logging (kills plants as water table rises into the root zone)

Question 13

Explain what monoculture practices is

Answer 13

• When one species is grown -> biodiversity is reduced
• use of fertilisers, pesticides, and herbicides to reduce the natural tenancy of the community to diversify.
• more prone to pest outbreaks and diseases as they do not have good ecological defense mechanisms.