Flashcards in Biodiversity (Chapter 18) Deck (44)
What is a species?
A group of organisms with a similar morphology and physiology, which can breed together to produce fertile offspring and are reproductively isolated from other species
What is an ecosystem?
A relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact
What is a habitat?
The place where a species lives within an ecosystem
What is a niche?
The role of an organism in an ecosystem
How do species live?
Species do not live in isolation - they share their living space with others to form communities of organisms which interact with each other and their environment
What does an organism's niche describe?
- Where it is, how it obtains energy and how it interacts with its physical environment and with other species
- In many ecosystems, there are similar niches that may be occupied by the same species e.g. herbivores in Savannah
What is biodiversity?
The degree of variation of life that forms in an ecosystem
What are the three levels of diversity in biodiversity?
1) the variation in ecosystems or habitats
2) the number of different species in the ecosystem and their relative abundance
3) the genetic variation within each species
What is species richness?
The number of species in a community
What is species diversity?
A measure of the evenness of the abundance of the different species, taking species richness into account
What leads to a greater species diversity?
The more species there are and the more evenly the number of organisms are distributed among the different species, the greater the species diversity
What is a characteristic of ecosystems with high species diversity?
They tend to be more stable than ones with limited diversity ∴ are more able to resist changes
What is genetic diversity?
The diversity of alleles within the genes in the genome of a single species
Describe the genes of all individuals of a species
All individuals of a species have the same genes, but they do not all have the same alleles of those genes
Why do genetic differences between populations of the same species exist?
Because populations may be adapted slightly differently in different parts of their range
Why is genetic diversity within each population important?
It provides populations with the ability to adapt to changes in biotic and abiotic factors e.g. competition with other species and changes in temperature
Why is biodiversity under threat in many aquatic and terrestrial ecosystems?
1) as the human population increases, more resources are taken from the environment and increasing quantities of waste are produced
2) ecosystems and species are being lost at an alarming rate, directly by humans and indirectly by humans through climate change
What are the 5 major threats to biodiversity?
1) habitat loss and degradation of the environment
2) climate change
3) excessive use of fertilisers and industrial/domestic forms of pollution
4) the overexploitation and unsustainable use of resources
5) the effect of invasive alien species on native species, especially on endemic species
How do the actions of humans lead to habitat loss?
1) the clearing of land for agriculture, housing, transport, leisure facilities and industry removes vegetation
2) ∴ many species of plant and animal either lose their habitats completely or their habitats become divided into smaller areas (habitat fragmentation)
3) endemic species on small islands are most at risk of extinction
What are the devastating effects of deforestation on some countries e.g. Madagascar?
- Lots of forest in southern hemisphere has been cut down and often replaced with cattle ranches and plantations of palm oil, which have much lower biodiversity
- Deforestation can lead to severe land degradation as a result of soil erosion once the vegetation is removed
Why is overfishing a problem?
- Many species of fish have been driven to near extinction by overfishing e.g. cod and herring
- The response to the steep decrease in large, predatory species is to fish further down the food chain, taking smaller fish that other animals e.g. sea birds and marine mammals depend on
- Fishing is an example of the overexploitation of resources
What is another example of the overexploitation of resources, other than overfishing?
The removal by logging companies of valuable trees e.g. teak and mahogany at a rate faster than they can regenerate
What is a keystone species?
Organisms that play a central role in an ecosystem e.g. sea otter and African bush elephant
What happens when a keystone species is lost?
The loss of a single species e.g. the sea otter, can have a devastating effect on the rest of its community and lead to catastrophic loss of other species (from the explosion in sea urchin numbers)
What happens to industrial and domestic waste in many countries?
1) it is processed to reduce its impact on the environment e.g. sewage is treated before it reaches aquatic ecosystems (rivers and the sea)
2) toxic industrial waste is collected and disposed of so that it cannot leak into the environment
How is pollution a major threat to many ecosystems?
Where waste is not processed and disposed of safely, ecosystems are polluted, often with substances that animals cannot metabolise or excrete
What is an example of how pollution can be a threat to ecosystems?
- Waste from factories including PCBs, used to flow directly into rivers without any form of treatment
- Even though PCBs are no longer used, they persist in the environment and have entered food chains
- Effects: the weakening of immune systems and reduction in fertility of birds + contributing to the deaths of seals in the North Sea from viral infection
Why is non-biodegradable plastic a major marine pollutant?
Animals e.g. dolphins and turtles, get caught in discarded fishing nets and die + turtles eat plastic bags, mistaking them for jelly fish
How can fertilisers have negative effects on the environment and biodiversity?
1) fertilisers that have not been absorbed by crop plants on low-lying farmland near coats drain into rivers and then into the sea
2) the extra nutrients that become available to river and marine ecosystems cause growth of producers e.g. algae
3) this often occurs faster than herbivorous organisms e.g. fish can feed on them to keep their growth under control
4) many of these algae produce toxic substances and their growth often unbalances food webs
5) excess growth of algae has catastrophic effects on coral reeds and hugely reduces biodiversity