4. Ecological systems, biodiversity and conservation Flashcards
The interactions of organisms with each other and with the environment in which they live are the basis of
ecosystem dynamics.
Dynamics simply refers to all the actions and activities that happen in an ecosystem
An ecosystem is dynamic which means that
changes are happening in it all the time, as interactions take place
what constantly flows through an ecosystem (2)
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
The components of an ecosystem that affect the
organisms within it can be divided into
biotic factors and abiotic factors.
The species that make up populations and communities within an ecosystem engage in activities such as (3)
capturing solar energy for photosynthesis,
capturing prey as food, and absorbing minerals
The energy that powers most ecosystems comes from
the sun
Energy which flows through ecosystems starts with
photosynthesis
the 2 types of competition in species
interspecific competition – competition between different species
intraspecific competition – competition between members of the same species
what happens If two species have identical niche requirements
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.
Cooperation exists at different levels. The best example of cooperation within a species is seen in
social insects such as ants, termites and honey bees.
altruism is when
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.
example of mutualism in coral reefs
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
example of mutualism in sharks
Sharks are often attended by pilot fish, which clean them of parasites that infest them.
The benefits to both species are obvious.
Biotic factors are ones that involve
other living organisms.
Biotic factors include (5)
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
Abiotic factors are
ones that involve non-living components of the environment
Abiotic factors include (11)
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
the abiotic factor temperature affects the rate of what?
affects the rate of metabolic reactions in both endothermic and ectothermic organisms
the abiotic factor light intensity affects the rate of what?
affects the rate of photosynthesis in plants and also the behaviour of animals
the abiotic factor oxygen concentration affects who?
affects any organism that respires aerobically
the abiotic factor carbon dioxide concentration affects what?
affects photosynthesising plants and algae
the abiotic factor water supply affects who?
affects all terrestrial organisms
the abiotic factor pH of water or soil affects what?
affects all organisms living in them
the abiotic factor of the availability of inorganic ions such as nitrate or potassium affects what?
affects the growth of plants
factors relating to the soil are known as
edaphic factors, such as aeration, size of soil particles, drainage and mineral content
the abiotic factor atmospheric humidity affects what?
affects the rate of water loss by evaporation from an organism’s body
the abiotic factor wind speed affects what?
affects transpiration rate of plants and can also greatly increase cooling effects if the environmental temperature is low
the abiotic factor wave action affects what?
wave action can damage organisms but also helps to move nutrients and gases around
The greatest solar energy input is in where?
in the tropics
Tropical ecosystems have high what?
high biodiversity and complex food webs
The rate at which plants assimilate energy from the Sun is called
gross primary productivity.
what has a major influence on gross primary productivity
The availability of water and the environmental temperature
The total amount of energy that
plants assimilate by photosynthesis is called
gross primary production
Gross primary production is measured how?
over a year of plant growth
Net primary production is
gross primary production minus the energy that plants use for respiration, growth, reproduction and survival
The distribution of primary production worldwide is related to
the temperature and moisture at different longitudes and latitudes on Earth’s surface
how is the productivity of hot, humid tropics and in drier, cooler regions?
In the hot, humid tropics, productivity is at its highest
In the drier, cooler regions of Earth, productivity is lower.
who produces the highest net primary production of all ecosystems?
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.
what have the greatest total area of the Earth’s surface?
oceans
To assimilate is to
use up molecules that have been absorbed or energy that has been absorbed.
explain the effect of wave action in the coral reefs
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.
Reefs can be damaged by wave action due to what?
the high winds in a hurricane.
example of the biotic factor of feeding in the coral reefs
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.
what is now thought to be vital to the survival of coral reef that has been seriously damaged.
queen parrotfish (Scarus vetula).
give an example of predation in coral reefs with barracuda
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.
example of a formidable predator of larger fish on a coral reef
Barracuda (Sphyraena spp
aquatic predators have evolved into
fast swimmers with a very rapid acceleration
example of parasitism on the reef
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
example of mutualism on the coral reef
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
Zooxanthellae are ________.
symbiotic algae that provide energy to many species of corals
single-celled algae
The bleaching of coral indicates what?
either the death or loss of the zooxanthellae.
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
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
sweeper tentacles are
tentacles that have an increased number of nematocysts and are specially elongated to ‘sting’ neighboring corals
High temperature in the coral reef is strongly associated with
extensive coral bleaching
Bleaching in corals is a
stress response that results when the coral-algae relationship breaks down
Bleaching also occurs in other animals that are engaged in symbiotic relationships with zooxanthellae, such as
foraminifera, sponges, anemones and giant clams
the effect of high temperature on the coral reef
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
oxygen concentration in the coral reefs
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.
effect of light intensity on the coral reefs
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.
effect of carbon dioxide in the coral reefs
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
Studies of seagrass beds that have been enriched by mineral ions running off agricultural land and sewage from urban areas show that
the food web is dramatically changed.
Figure 4.6 Control processes in a Caribbean reef ecosystem and impacts of global warming and seawater acidification
chegg
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
predict the impact of these in the future.
warming and acidification will have a major impact on reef ecosystems. This may be so severe that it has been suggested that
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.
The impact of humans on ecosystems
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.
