Chapter 5: Changing Ecosystems Flashcards
What is succession?
The progressive change of communities over time
What are the two main modes of succession?
Primary and secondary?
What is primary succession?
The colonization of plants in a barren place
What is a pioneer plant?
A plant capable of invading bare sites, such as a newly exposed soil surface
Why are pioneer plants effective colonizers?
They can live under extreme conditions, able to grow in poor soils with low nutrient levels, and have the ability to fix nitrogen into the soil through their relationship with specialized bacteria growing in root nodules. They also have effective seed dispersal, and rapid growth, and rapid reproduction. They are normally small and photosynthetic.
What is an r-selected species?
A fast-growing and reproducing organism, often the first to occupy unused resources and living space. They are consistent with a J-curve of exponential growth (pioneer species)
What is secondary succession?
The recolonization of disturbed plant communities, regaining equilibrium, although the number and kinds of organisms present may be different
What is a climax community?
The end-point in a community succession where the community has become relatively stable, e.g. old-growth forests and rainforests
What are K-selected species?
A slow-growing, long-lived typical of those in a climax community
What limits a succession from reaching a climax?
Examples include: fire and selective grazing by herbivores helps to create conditions that allow grasslands to persist
How to predict the stage of succession?
Refer to table 5.1.1
What was the original supercontinent?
Pangea
What were the two resulting pieces of Pangea after it split?
Laurasia and Gondwana
What caused Australia’s biota distinctive characteristics?
Originally being Gondwana, it separated from Pangea
What can be used to observe changes in abiotic factors?
Studying soils, rocks, and ice cores
How can ice cores be used to observe past abiotic factors?
By analyzing the air trapped in the ice, the climate and gasses present can be observed
How can successional changes be precited?
By collecting data and creating models through sampling and census collection
What was the impact of European colonization on Australia?
Due to the Europeans imposing agricultural practices unsuited to the land, disregarding fire management tools, and disregarding the well-adapted animals and their food sources, the environment saw a great decline in sustainability
What was the impact of sheep on the Australian environment?
Plants were disappearing, hills were slipping, springs of saltwater were appearing, and erosion from rainfall was becoming evident
What has contributed to the extinction of thousands of species?
Destruction of habitats, changes to the atmosphere and water, the stripping of vegetation, and the exploitation of wildlife have all contributed to the extinction of thousands of species
What are some main causes for the current unsustainable environment?
Urbanization, habitat destruction, land and soil degradation, salinity, and monoculture practices
Since 1750, how much forest and vegetation has been cleared?
20% of forests have been cleared and 90% of vegetation has been cleared
What is habitat fragmentation?
The process by which areas of habitat are lost, resulting in a large continuous habitat being broken up into smaller, more isolated habitats
How do agricultural animals (sheep and cattle) impact the environment?
Due to hard hooves, they compact the soil which promoted invasive species, reducing tree cover and the topsoil becomes more exposed to abiotic elements (wind and rain). Due to selective grazing, they allow for specific species to grow, reducing biodiversity. Gradually changing the environment
What other factors can impact the topsoil of an environment?
Past land clearances, the move to shallow-rooted pastoral grasses, the overuse of fertilizers and heavy machinery
What is salinization?
The increased salt concentration
What is monoculture?
The agricultural practice of growing a single crop or plant species over a wide area for a large number of consecutive years
What are the impacts of monoculture?
Extensive use of fertilizers, pesticides, and herbicides; the spread of disease and susceptibility to changing environmental conditions
