4. Ecological systems, biodiversity and conservation

Question 1

The interactions of organisms with each other and with the environment in which they live are the basis of

Answer 1

ecosystem dynamics.

Dynamics simply refers to all the actions and activities that happen in an ecosystem

Question 2

An ecosystem is dynamic which means that

Answer 2

changes are happening in it all the time, as interactions take place

Question 3

what constantly flows through an ecosystem (2)

Answer 3

1) energy from one organism to another and between organisms and the non-living environment.
2) Materials pass between the environment and the organisms, and between the different organisms in the ecosystem

Question 4

The components of an ecosystem that affect the

organisms within it can be divided into

Answer 4

biotic factors and abiotic factors.

Question 5

The species that make up populations and communities within an ecosystem engage in activities such as (3)

Answer 5

capturing solar energy for photosynthesis,

capturing prey as food, and absorbing minerals

Question 6

The energy that powers most ecosystems comes from

Answer 6

the sun

Question 7

Energy which flows through ecosystems starts with

Answer 7

photosynthesis

Question 8

the 2 types of competition in species

Answer 8

interspecific competition – competition between different species

intraspecific competition – competition between members of the same species

Question 9

what happens If two species have identical niche requirements

Answer 9

the competition between them will be intense

This rarely means that they will fight each other, but the less successful species will starve or not find anywhere to reproduce.

Question 10

Cooperation exists at different levels. The best example of cooperation within a species is seen in

Answer 10

social insects such as ants, termites and honey bees.

Question 11

altruism is when

Answer 11

Individuals work together for the benefit of the colony, even when that means some individuals do not get a chance to breed, as is the case with soldier ants and worker bees.

Question 12

example of mutualism in coral reefs

Answer 12

The polyps of many coral species contain single-celled algae called zooxanthellae, which photosynthesise.

The algae gain protection, carbon dioxide and nitrogenous waste from the polyps and in exchange provide carbohydrate in the form of sugars.

Coral grows near the surface of the water, so providing their algae with sufficient light

Question 13

example of mutualism in sharks

Answer 13

Sharks are often attended by pilot fish, which clean them of parasites that infest them.

The benefits to both species are obvious.

Question 14

Biotic factors are ones that involve

Answer 14

other living organisms.

Question 15

Biotic factors include (5)

Answer 15

feeding of herbivores on plants or algae

predation, in which one organism (the predator) kills and eats another (the prey)

parasitism, in which one organism (the parasite) lives in close association with an organism of a different species (the host) and does it harm

mutualism

competition

Question 16

Abiotic factors are

Answer 16

ones that involve non-living components of the environment

Question 17

Abiotic factors include (11)

Answer 17

temperature 
light intensity 
oxygen concentration
carbon dioxide concentration
water supply
pH
availability of inorganic ions
factors relating to the soil
atmospheric humidity
wind speed
wave action

Question 18

the abiotic factor temperature affects the rate of what?

Answer 18

affects the rate of metabolic reactions in both endothermic and ectothermic organisms

Question 19

the abiotic factor light intensity affects the rate of what?

Answer 19

affects the rate of photosynthesis in plants and also the behaviour of animals

Question 20

the abiotic factor oxygen concentration affects who?

Answer 20

affects any organism that respires aerobically

Question 21

the abiotic factor carbon dioxide concentration affects what?

Answer 21

affects photosynthesising plants and algae

Question 22

the abiotic factor water supply affects who?

Answer 22

affects all terrestrial organisms

Question 23

the abiotic factor pH of water or soil affects what?

Answer 23

affects all organisms living in them

Question 24

the abiotic factor of the availability of inorganic ions such as nitrate or potassium affects what?

Answer 24

affects the growth of plants

Question 25

factors relating to the soil are known as

Answer 25

edaphic factors, such as aeration, size of soil particles, drainage and mineral content

Question 26

the abiotic factor atmospheric humidity affects what?

Answer 26

affects the rate of water loss by evaporation from an organism’s body

Question 27

the abiotic factor wind speed affects what?

Answer 27

affects transpiration rate of plants and can also greatly increase cooling effects if the environmental temperature is low

Question 28

the abiotic factor wave action affects what?

Answer 28

wave action can damage organisms but also helps to move nutrients and gases around

Question 29

The greatest solar energy input is in where?

Answer 29

in the tropics

Question 30

Tropical ecosystems have high what?

Answer 30

high biodiversity and complex food webs

Question 31

The rate at which plants assimilate energy from the Sun is called

Answer 31

gross primary productivity.

Question 32

what has a major influence on gross primary productivity

Answer 32

The availability of water and the environmental temperature

Question 33

The total amount of energy that

plants assimilate by photosynthesis is called

Answer 33

gross primary production

Question 34

Gross primary production is measured how?

Answer 34

over a year of plant growth

Question 35

Net primary production is

Answer 35

gross primary production minus the energy that plants use for respiration, growth, reproduction and survival

Question 36

The distribution of primary production worldwide is related to

Answer 36

the temperature and moisture at different longitudes and latitudes on Earth’s surface

Question 37

how is the productivity of hot, humid tropics and in drier, cooler regions?

Answer 37

In the hot, humid tropics, productivity is at its highest

In the drier, cooler regions of Earth, productivity is lower.

Question 38

who produces the highest net primary production of all ecosystems?

Answer 38

The open ocean produces the highest net primary production of all ecosystems even though the net primary productivity per square metre is relatively low.

Oceans have the greatest total area of the Earth’s surface.

Question 39

what have the greatest total area of the Earth’s surface?

Answer 39

oceans

Question 40

To assimilate is to

Answer 40

use up molecules that have been absorbed or energy that has been absorbed.

Question 41

explain the effect of wave action in the coral reefs

Answer 41

Reefs can be damaged by wave action due to the high winds in a hurricane.

This is destructive but does not necessarily mean that the reef is permanently damaged as we will see below. Wave action is not all destructive.

Normal wave action is important in constantly causing water movement, bringing oxygen to respiring organisms and plankton to stationary organisms that feed on it, such as anemones.

Question 42

Reefs can be damaged by wave action due to what?

Answer 42

the high winds in a hurricane.

Question 43

example of the biotic factor of feeding in the coral reefs

Answer 43

Following the death of the coral; either from severe wave action in a hurricane or after attack by a large population of sea urchins which eat coral, there is a massive growth of seaweed, totally covering the area.

The queen parrotfish parrotfish feed actively on the seaweed.

Without the fish reducing seaweed growth (from 100% to 40%), coral is not able to re-establish in this area.

If the populations of the different species of parrotfish are low due to overfishing, only about 5% of reef is grazed down sufficiently to allow coral to grow again and it does not recover.

Question 44

what is now thought to be vital to the survival of coral reef that has been seriously damaged.

Answer 44

queen parrotfish (Scarus vetula).

Question 45

give an example of predation in coral reefs with barracuda

Answer 45

Barracuda is a predator in the coral reef that patrol outer reef areas in large schools and have evolved into fast swimmers with a very rapid acceleration who kill their prey using conical, razor-sharp teeth.

The selection pressure of this on their prey has resulted in a variety of defences against the predation.

• schooling with better-armoured fish
• hiding in crevices when a predator is noticed.
• the accumulation of toxin derived from ingested protoctists or by eating fish that have themselves eaten protoctists.

However, many reef predators are immune to the toxins. On the other hand, humans are not immune, so these toxins can cause serious poisoning when eating some fish.

Question 46

example of a formidable predator of larger fish on a coral reef

Answer 46

Barracuda (Sphyraena spp

Question 47

aquatic predators have evolved into

Answer 47

fast swimmers with a very rapid acceleration

Question 48

example of parasitism on the reef

Answer 48

isopods (sealice) that are found on fish skin.

These isopods reduce the vigour of the fish they parasitise because they eat skin and blood.

In a study of fish caught for human food in the southern Caribbean, 0.9% of the fish had isopod parasites. This makes an interesting comparison with the rates of sealice infection in fish that are farmed, which are very much higher than this unless there is chemical control of the sealice.

The reef ecosystem is complex and there are clearly controls that generally keep parasite populations to relatively low levels, controls that we cannot apply to fish being farmed

Question 49

example of mutualism on the coral reef

Answer 49

between organisms that make up the reef-building corals- a colony of multicellular cnidarians is associated with zooxanthellae living inside the animals’ tissues (for example, Symbiodinium spp.).

These zooxanthellae photosynthesise and provide carbohydrates for the coral. The coral supports and protects the zooxanthellae. The pigments the zooxanthellae use to capture light give the coral a range of colours. Near the surface of the sea, the high light intensity here allows high rates of growth of some corals, for example elkhorn coral

The bleaching of coral indicates either the death or loss of the zooxanthellae. This is a serious disturbance of the mutualistic relationship and is sometimes observed taking place over a wide area of reef. As coral reefs are under a number of threats, coral bleaching is of concern and is being studied to find the causes

Question 50

Zooxanthellae are ________.

Answer 50

symbiotic algae that provide energy to many species of corals

single-celled algae

Question 51

The bleaching of coral indicates what?

Answer 51

either the death or loss of the zooxanthellae.

Question 52

Competition is common on the coral reef.

Two different species in the same area of reef are quite likely to both be competing for a particular resource that is in short supply

give an example of competition in the coral reef

Answer 52

The highest number of different species of coral occurs on the crests and outer slopes of reef which are the areas that are exposed to damaging storms.

After storm damage, there is recolonisation by many species of coral.

As the area becomes filled, the corals will compete for invertebrate food and especially light. Following storm damage, you can observe corals overshadowing and overgrowing others or even attacking neighbouring corals.

Attacks can be by

• sweeper tentacles – tentacles that have an increased number of nematocysts and are specially elongated to ‘sting’ neighboring corals.
• soft corals uses chemical warfare by the release of inhibitory chemicals, such as terpenoids

Question 53

sweeper tentacles are

Answer 53

tentacles that have an increased number of nematocysts and are specially elongated to ‘sting’ neighboring corals

Question 54

High temperature in the coral reef is strongly associated with

Answer 54

extensive coral bleaching

Question 55

Bleaching in corals is a

Answer 55

stress response that results when the coral-algae relationship breaks down

Question 56

Bleaching also occurs in other animals that are engaged in symbiotic relationships with zooxanthellae, such as

Answer 56

foraminifera, sponges, anemones and giant clams

Question 57

the effect of high temperature on the coral reef

Answer 57

High temperature causes coral bleaching

Quite often, the coral remains alive after this event

Bleaching tends to occur if the sea temperature goes 1°C higher than the mean maximum summer temperature but sea temperature is expected to rise due to climate change

corals are monitoring performance of the zooxanthellae at all times and if they are under performing they might be expelled by the cnidaria so that another strain or strains of zooxanthellae can be acquired that are better performing.

Bleaching is always patchy, showing that there are other factors than just temperature affecting it.

coral and the zooxanthellae have evolved to tolerate the temperature ranges that they have experienced in the past.

With temperatures rising, it is expected that the coral and zooxanthellae will evolve to be better adapted to these higher temperatures

Question 58

oxygen concentration in the coral reefs

Answer 58

The oxygen concentration of the water of the reef varies quite a lot (3-9cm3 dm-3).

Water turbulence mixes surface water, which dissolves oxygen from the air, with seawater below the surface, so the degree of turbulence will affect oxygen concentration in the water around a coral reef.

Oxygen is not particularly soluble in water and aquatic environments may be affected by oxygen shortage at times. Higher temperatures reduce oxygen solubility.

Question 59

effect of light intensity on the coral reefs

Answer 59

Light intensity has an impact on oxygen supply through the photosynthesis of the zooxanthellae in the corals on a bright day.

If the water is not cloudy due to sediment, the coral releases oxygen into the water at a rate greater than it can dissolve and bubbles of oxygen can be seen on the coral.

At low light intensities and at night the respiration of all organisms of the reef, including the coral and the zooxanthellae, will reduce the oxygen concentration of the water.

This may affect the most active of the fish which have a high demand for oxygen when swimming rapidly.

Question 60

effect of carbon dioxide in the coral reefs

Answer 60

In seawater, carbon dioxide concentration is rarely limiting, though it is a raw material for photosynthesis.

Seawater contains much dissolved hydrogencarbonate (HCO3 - ) and carbonic acid (H2 CO3 ). If dissolved carbon dioxide is used up, some hydrogencarbonate breaks down to release carbon dioxide. Then some carbonic acid breaks down to release hydrogencarbonate.

For a coral reef, the problem with carbon dioxide is that there is generally too much. The rising atmospheric levels of carbon dioxide cause a rise in hydrogencarbonate and carbonic acid in seawater.

This lowers the pH of the water and is referred to as acidification.

the rise in carbon dioxide levels over the past 300 years has caused a 40% reduction in the synthesis of the main mineral used by reef building corals. If it continues this way, many reefs will stop growing, and will then turn from coraldominated reefs to algal-dominated reefs

Question 61

Studies of seagrass beds that have been enriched by mineral ions running off agricultural land and sewage from urban areas show that

Answer 61

the food web is dramatically changed.

Question 62

Figure 4.6 Control processes in a Caribbean reef ecosystem and impacts of global warming and seawater acidification

Answer 62

chegg

Question 63

If you study an ecosystem in this way by looking at the control processes and identify the processes that are most affected by such things as global warming and its associated acidification of seawater, it becomes more possible to

Answer 63

predict the impact of these in the future.

Question 64

warming and acidification will have a major impact on reef ecosystems. This may be so severe that it has been suggested that

Answer 64

most reef ecosystems may be lost in the not too distant future. If so, there will be serious consequences for reef-associated fisheries, tourism, coastal protection and the human communities dependent on these.

Question 65

The impact of humans on ecosystems

Answer 65

The impact of humans on ecosystems contrasts with the observation that ecosystems with less human interference appear to be quite stable.

It has been suggested that this is a consequence of the high complexity of the ecosystem.

Small disturbances affect organisms within the ecosystem, but recovery to former conditions is possible.

If an ecosystem is seriously disturbed by the complete removal of one or more significant species from that ecosystem, it can often be followed by extreme instability with large fluctuations in the population sizes of species that remain.

Understanding what stabilises ecosystems will help us prevent excessive damage to the environment and the impact of that on human societies.