Biodiversity (Chapter 18)

Question 1

What is a species?

Answer 1

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

Question 2

What is an ecosystem?

Answer 2

A relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact

Question 3

What is a habitat?

Answer 3

The place where a species lives within an ecosystem

Question 4

What is a niche?

Answer 4

The role of an organism in an ecosystem

Question 5

How do species live?

Answer 5

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

Question 6

What does an organism’s niche describe?

Answer 6

• 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

Question 7

What is biodiversity?

Answer 7

The degree of variation of life that forms in an ecosystem

Question 8

What are the three levels of diversity in biodiversity?

Answer 8

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

Question 9

What is species richness?

Answer 9

The number of species in a community

Question 10

What is species diversity?

Answer 10

A measure of the evenness of the abundance of the different species, taking species richness into account

Question 11

What leads to a greater species diversity?

Answer 11

The more species there are and the more evenly the number of organisms are distributed among the different species, the greater the species diversity

Question 12

What is a characteristic of ecosystems with high species diversity?

Answer 12

They tend to be more stable than ones with limited diversity ∴ are more able to resist changes

Question 13

What is genetic diversity?

Answer 13

The diversity of alleles within the genes in the genome of a single species

Question 14

Describe the genes of all individuals of a species

Answer 14

All individuals of a species have the same genes, but they do not all have the same alleles of those genes

Question 15

Why do genetic differences between populations of the same species exist?

Answer 15

Because populations may be adapted slightly differently in different parts of their range

Question 16

Why is genetic diversity within each population important?

Answer 16

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

Question 17

Why is biodiversity under threat in many aquatic and terrestrial ecosystems?

Answer 17

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

Question 18

What are the 5 major threats to biodiversity?

Answer 18

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

Question 19

How do the actions of humans lead to habitat loss?

Answer 19

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

Question 20

What are the devastating effects of deforestation on some countries e.g. Madagascar?

Answer 20

• 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

Question 21

Why is overfishing a problem?

Answer 21

• 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

Question 22

What is another example of the overexploitation of resources, other than overfishing?

Answer 22

The removal by logging companies of valuable trees e.g. teak and mahogany at a rate faster than they can regenerate

Question 23

What is a keystone species?

Answer 23

Organisms that play a central role in an ecosystem e.g. sea otter and African bush elephant

Question 24

What happens when a keystone species is lost?

Answer 24

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)

Question 25

What happens to industrial and domestic waste in many countries?

Answer 25

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

Question 26

How is pollution a major threat to many ecosystems?

Answer 26

Where waste is not processed and disposed of safely, ecosystems are polluted, often with substances that animals cannot metabolise or excrete

Question 27

What is an example of how pollution can be a threat to ecosystems?

Answer 27

• 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

Question 28

Why is non-biodegradable plastic a major marine pollutant?

Answer 28

Animals e.g. dolphins and turtles, get caught in discarded fishing nets and die + turtles eat plastic bags, mistaking them for jelly fish

Question 29

How can fertilisers have negative effects on the environment and biodiversity?

Answer 29

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

Question 30

How does pollution of air lead to problems for aquatic and terrestrial ecosystems?

Answer 30

1) the combustion of fields with a high sulfur content e.g. coal leads to high [SO2] in the atmosphere, which reacts with water vapour to fall as acid rain
2) acid rain destroys vegetation and leads to the acidification of aquatic ecosystems in parts of the world downwind of highly industrialised areas
3) few animals can survive or breed in waters of low pH ∴ biodiversity decreases markedly and ecosystems are at risk

Question 31

What has lead to the build up of greenhouse gases?

Answer 31

1) industrialisation and the extraction/combustion of fossil fuels have lead to an increase in the concentration of greenhouse gases in the atmosphere (CO2 and methane)
2) high emissions if methane are associated with cattle and rice farming and the breakdown, under anaerobic conditions, of organic waste in landfill sites

Question 32

What is the build up of greenhouse gases leading to?

Answer 32

Climate change

Question 33

What is global warming likely to produce?

Answer 33

1) changes in the distribution of terrestrial ecosystems as organisms are expected to migrate north or south to cooler latitudes and to higher altitudes
2) ∴ there will be competition between migrating organisms and species in existing communities

Question 34

Why are corals at risk?

Answer 34

1) the acidification of oceans is problem for coral reeds and species that make their skeletons and shells from CaCO3 e.g. many molluscs
2) corals are very sensitive to temperature increases bc the algae that live inside the polyps tend to leave the corals if the temperature remains high for a period of time - this leads to coral bleaching (coral turning white), which can lead to the death of the coral

Question 35

Why are coral reefs important to protect?

Answer 35

1) they are one of the most diverse ecosystems on Earth
2) we rely on them to provide protection for many coastlines
3) a large proportion of coral reefs have already been destroyed or degraded by overfishing, mining and fertiliser run-off

Question 36

What problems will the rise in sea-levels associated with global warming bring for coastal ecosystems (some of the most productive on Earth)?

Answer 36

1) some ecosystems will become even more restricted in their range than is currently the case e.g. ecosystems associated with high altitudes will retreat higher up mountains
2) some will be even more fragmented

Question 37

Why is the increasing frequency of natural disasters e.g. typhoons a problem?

Answer 37

1) following typhoons, flooding increases the concentration of nutrients in coastal waters
2) this encourages growth of phytoplankton which proves food for the larvae of the crown-of-thorns starfish - huge numbers of adults than eat the coral
3) eventually the number of starfish decrease and the coral regrows
4) if these population explosions happen more frequently than ever 10 years or so, the coral may not have time to recover

Question 38

What are the moral and ethical reasons that biodiversity matters?

Answer 38

1) we share our planets with a huge range of other organisms and we have no right to drive them to extinction
2) humans have custody of the Earth and ∴ should value and protect the organisms that share the planet with us

Question 39

Why is biodiversity important for an ecosystem?

Answer 39

• In general, the higher the diversity of an ecosystem, the less likely it is to be unbalanced by changes in conditions or threats e.g. pollution
• All the organisms in an ecosystem interact in many different ways and if one key species disappears, this can affect the whole community
• We are part of many ecosystems and rely on them in many ways

Question 40

Why is biodiversity important for humans and medicine?

Answer 40

• Many of the drugs that we use originate from living organisms ∴ ecosystems are of direct value to humans
• e.g. antibiotics isolated from fungi and bacteria + anti-cancer drugs isolated from plants e.g. Madagascan periwinkle and Pacific yew tree (paccitaxel)
• There is much interest in cataloguing plants used in traditional Chinese and Indian medicines to see if they can provide drugs that be be mass-produced
• If biodiversity disappears, we are losing species the we do not yet know could be beneficial to us

Question 41

What are the aesthetic reasons that biodiversity matters?

Answer 41

1) many people fain pleasure from studying or just appreciating the natural world, which provides much inspiration for artists, photographers, poets, writers and other creative people
2) wildlife is a source of income for many countries e.g. in Belize and Malaysia ecotourism has increased in popularity - this form of tourism provides employment and contributes to the economies of these nations e.g. from encouraging tourists to visit their National Parks

Question 42

How does biodiversity allow us to widen the diversity of cultivated crops?

Answer 42

• Wild relatives of crop plants can provide the genetic resources we might need to widen the genetic diversity of cultivated crops e.g. maize if they are affected by disease or by other catastrophes as wild relatives have much more genetic diversity than crop plants
• Wild species of e.g. rice and potato can be interbred with cultivated crops to give varieties with e.g. disease resistance by introducing alleles (also by gene tech)

Question 43

How is biodiversity among microorganisms important?

Answer 43

• Microorganisms are the source of antibiotics and many other useful products e.g. Taq polymerase discovered in Thermus aquatics and is now mass produced for use in PCR
• There are likely to be other compounds, especially enzymes, in archaeans that live in extreme conditions

Question 44

What are 4 other service of biodiversity?

Answer 44

1) forests and peat bogs absorb CO2 and may help to reduce the effect of increases in CO2 in the atmosphere
2) organic waste material added to waters is broken down by microorganisms
3) the transpiration of plants contributes to the water cycle, providing us with drinking and irrigation water
4) termites, ants + species of fungi and bacteria recycle elements e.g. C, N, S and P - without this recycling, the supply of nitrates, sulfates and phosphates for plants would become limiting ∴ plants growth would slow and there would be less food available for organisms in other trophic levels