IB Biology HL: Ecology & Conservation

Explain why nutrient cycling is necessary for an ecosystem. (3)

- The amount of matter on earth stays constant, so CO2, O2, etc. must be recycled. - Decomposers break proteins from dead organisms into ammonia, which is then converted to useful nitrates for plants. - This process allows for a constant supply of inorganic nutrients.

Explain the greenhouse effect (include short and longwave radiation) and how it contributes to global warming. (4)

- The greenhouse effect functions to trap heat within the atmosphere and hence prevent rapid temperature fluctuations. - Incoming radiation from the sun is shorter wave radiation (ultraviolet radiation and the visible spectrum). - The surface of the Earth absorbs shortwave radiation and re-emits it at a longer wavelength (i.e. infra-red / heat). - Greenhouse gases absorb and re-radiate this longwave radiation and hence retain the heat within the atmosphere.

Explain the relationship between rising atmospheric carbon dioxide concentrations and global temperatures. (6)

- The incoming radiation from the sun is shortwave ultraviolet and visible radiation. - Some of this radiation is absorbed by the earth's atmosphere. - Some of the radiation is reflected back into space by the earth's surface. The radiation which is reflected back into space is called infrared radiation and has a longer wavelength. - The greenhouse gases in the atmosphere absorb some of this infrared radiation and re-reflect it back towards the earth. - This causes the greenhouse effect and results in an increase in average mean temperatures on earth. - A rise in greenhouse gases results in an increase of the greenhouse effect which can be disastrous for the planet.

Outline potential threats to coral reefs due to increased levels of dissolved carbon dioxide. (8)

- The oceans are a major carbon sink and absorb roughly a third of all human-produced CO2 emissions. CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise. - Carbon dioxide will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate. - H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate. - With less free carbonate ions in the water, marine organisms are less able to produce calcium carbonate (via calcification). - Calcium carbonate is used to form the hard exoskeleton of coral and is also present in the shells of certain mollusks. Hence, increasing concentrations of dissolved carbon dioxide threaten the viability of coral reefs and certain mollusks. - Rising levels of atmospheric carbon dioxide are causing a decrease in the pH of ocean water (ocean acidification). - The decrease in ocean pH is predicted to threaten the survival of marine organisms that require calcium carbonate. - Corals grow in colonies of many individual 'polyps' which live in a co-dependent relationship with single-celled algae that live within their tissues. Environmental stresses such as an increase in sea temperature force the coral polyps to eject the algae. As a result, corals lose their color and their source of food and energy (coral bleaching).

Explain how coal, oil and gas are formed.

- Under the right conditions, peat can eventually be transformed into coal (involves long periods of time, pressure, and heat). - Large potential energy due to hydrocarbon chains. - Similar transformations can lead to crude oil and natural gas (other fossil fuels).

State the factors that determine the impact of a greenhouse gas. (2)

1. Ability to absorb long-wave radiation. - Gases that have a greater capacity to absorb long-wave radiation will have a greater warming impact (per molecule). 2. Concentration in the atmosphere. - The greater the concentration of a gas, the greater its warming impact will be within the atmosphere. - The concentration of a gas will be determined by both its rate of release and persistence within the atmosphere.

Ecosystem

A biological community of interacting organisms and their physical environment.

Species

A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.

Community

A group of populations living and interacting in an area.

Describe how you could set up a sealed mesocosm to try and establish sustainability. (3)

A terrarium can be created using a glass or plastic bottle with a lid, according to the following steps: 1. Building a verdant foundation. - Add a bottom layer of pebbles, gravel or sand - this layer exists for drainage (smaller vessels require thinner rock layers). - Add a second thin layer of activated charcoal - this will prevent mold and help to aerate the soil Spread a thin cover of sphagnum moss (or use an organic coffee filter) to create a barrier between the lower layers and soil. - The final layer is the pre-moistened growing medium (i.e. potting mix). 2. Selecting the right plants. - Ideally, choose plants that are both slow growing and thrive in a bit of humidity (e.g. most ferns, club moss, etc.). - Inspect the plant thoroughly for any signs of disease or insects before introducing to the terrarium. 3. Maintaining appropriate conditions. - Ensure the terrarium is placed in a location that provides a continuous source of light. - Locate the terrarium in a place that does not experience fluctuating temperature conditions (i.e. avoid direct sunlight). - Do not initially over-water the plants - once the right humidity is established, a terrarium can go months without being watered. - Occasional pruning may be required - however, as the level of soil nutrients decrease, plant growth should slow down.

Population

All the organisms of the same group or species, which live in a particular geographical area, and have the capability of interbreeding.

Heterotroph

An organism deriving its nutritional requirements from complex organic substances.

Consumer

An organism that generally obtains food by feeding on other organisms or organic matter due to lack of the ability to manufacture own food from inorganic sources; a heterotroph.

Autotroph

An organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.

Describe how corals and mollusks relate to carbon and limestone.

Animals such as reef-building corals and mollusks have​ hard parts that are composed of calcium carbonate and can become fossilized in limestone.

Describe how global temperatures and climate patterns are influenced by the concentration of greenhouse gases. (3)

As these gases trap heat, increases in greenhouse gas concentrations should correlate with an increase in global temperature. Long-term weather patterns (climate) may also be influenced by greenhouse gas concentrations. Scientists predict that increases in greenhouse gas concentrations will lead to an enhanced greenhouse effect, resulting in: - More frequent extreme weather conditions (e.g. heat waves, cyclones, more powerful tropical storms, etc.). - Some areas to become more drought affected, while other areas become more prone to periods of heavy rainfall. - Changes to circulating ocean currents - which may cause longer El Nino (warming) and La Nina (cooling) events.

What is produced by the combustion of biomass and fossilized organic matter?

Carbon dioxide

Estimate carbon fluxes due to processes in the carbon cycle.

Carbon fluxes describe the rate of exchange of carbon between the various carbon sinks/reservoirs. There are four main carbon sinks: lithosphere (earth crust), hydrosphere (oceans), atmosphere (air), biosphere (organisms). The rate at which carbon is exchanged between these reservoirs depends on the conversion processes involved: - Photosynthesis: removes carbon dioxide from the atmosphere and fixes it in producers as organic compounds. - Respiration: releases carbon dioxide into the atmosphere when organic compounds are digested in living organisms. - Decomposition: releases carbon products into the air or sediment when organic matter is recycled after the death of an organism. - Gaseous dissolution: the exchange of carbon gases between the ocean and atmosphere. - Lithification: the compaction of carbon-containing sediments into fossils and rocks within the Earth's crust (e.g. limestone). - Combustion: releases carbon gases when organic hydrocarbons (coal, oil, and gas) are burned as a fuel source. Because carbon fluxes are large and based on measurements from many different sources, estimates have large uncertainties.

Describe how chemical energy flows through food chains.

Chemical energy in carbon compounds flows through food chains by means of feeding. - Producers always occupy the first trophic level in a feeding sequence. - Primary consumers feed on producers and hence occupy the second trophic level. - Further consumers (e.g. secondary, tertiary, etc.) may occupy subsequent trophic levels.

Evaluate claims that human activities are not causing climate change. (4)

Claim 1: Climate has changed in the past and current trends merely reflect the Earth's natural climatic cycle. - Climate changes do occur naturally, but usually not as abruptly as what is seen currently. - When global warming occurred abruptly in the past, it was always highly destructive to life (e.g. Permian mass extinction). - Atmospheric CO2 levels positively correlate to average global temperatures and are currently at the highest levels ever recorded. Claim 2: Climate change is being caused by solar activity and the effect of greenhouse gas emissions is negligible. - Over the last 35 years the sun has shown a slight cooling trend, however, average global temperatures have increased. - There is no evidence to support a correlation between solar irradiance and current global temperature trends. Claim 3: Certain changes in climate conditions cannot be linked to greenhouse gas emissions. - The overall pattern of change in sea levels will be influenced by the period of time over which the data is collected. - While sea levels did increase preceding the industrial revolution, this rise in sea levels followed a preceding period of decrease. - The rate at which sea levels have risen in the past 30 years is greater than that seen in the last 200 years. Claim 4: Increases in greenhouse gas concentrations in the atmosphere will not be enough to cause significant climate change. - The reason why carbon dioxide is so important to the environment is that there is so little of it. - Living things require constant internal environments (homeostasis) - small external changes can have big impacts on viability.

Classify the following as either autotroph, consumer, detritivore or saprotroph (there may be more than one correct choice): mushroom, alligator, palm tree, algae, and dung beetle.

Detritivore/consumer, consumer, , autotroph, detritivore/consumer, detritivore/counsumer.

Detritivores vs. saprotrophs

Detritivore: an organism that ingests non-living organic matter. Saprotroph: an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.​

Explain why there is a limit to the length of food chains and the biomass of higher trophic levels.

Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

Explain how methane is produced.

Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuse into the atmosphere or accumulates in the ground.

Describe how methane can contribute to CO2 levels in the atmosphere.

Methanogens are archaean microorganisms that produce methane (CH4) as a metabolic by-product in anaerobic conditions. Anaerobic conditions where methanogens may be found include: - Wetlands (e.g. swamps and marshes) - Marine sediments (e.g. in the mud of lake beds) - The digestive tract of ruminant animals (e.g. cows, sheep, goats) Methanogens produce methane from the by-products of anaerobic digestion, principally acetic acid and carbon dioxide. Methane may either accumulate under the ground or diffuse into the atmosphere.

Describe how peat forms.

Peat forms when plant material does not fully decay in acidic and anaerobic conditions. It is composed mainly of wetland vegetation: principally bog plants including mosses, sedges, and shrubs.

State the role of photosynthesis in an ecosystem.

Photosynthesis converts light energy to chemical energy stored in carbon compounds.

Ecology

The branch of biology that deals with the relations of organisms to one another and to their physical surroundings.

Habitat

The natural home or environment of an animal, plant, or another organism.

Outline the precautionary principle.

The precautionary principle holds that, if the effects of a human-induced change would be very large, perhaps catastrophic, those responsible for the change must prove that it will not do harm before proceeding.

List the greenhouse gases and identify which 2 contribute the most to global warming.

Water vapor, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons and hydrofluorocarbons. - Two most abundant are water vapor and CO2.

What is the best definition of the greenhouse effect in the Earth's atmosphere? a. A naturally occurring effect by which longer wavelength radiation is trapped b. An effect of pollution by which longer wavelength radiation is trapped c. An effect of pollution by which shorter wavelength radiation is trapped d. A naturally occurring effect by which shorter wavelength radiation is trapped

a. A naturally occurring effect by which longer wavelength radiation is trapped

What components are needed to make an ecosystem? a. Producers and consumers only b. A community and its abiotic environment c. Producers, consumers and decomposers only d. A community and its source of energy and nutrients

b. A community and its abiotic environment

In a pond, two species of fish feed on insects and worms. The insects feed on the green plants that live in the water. What constitutes a population in this ecosystem? a. All the fish b. All the fish of one species c. All the animals d. All the living organisms

b. All the fish of one species

Which hypothesis is supported by evidence from ecological research? a. Decomposers help to recycle energy from food chains. b. Producers use nutrients that decomposers help to recycle. c. Producers depend upon consumers more than on decomposers. d. Decomposers are the final stage in the food chain (the highest trophic level).

b. Producers use nutrients that decomposers help to recycle.

Global warming threatens the survival of Arctic foxes. Which of the following factors could be involved? I. Competition with other fox species spreading north II. Reduction in numbers of prey species of Arctic foxes III. Decrease in oxygen availability to Arctic foxes a. I only b. II and III only c. I and II only d. I, II and III

c. I and II only

If the flow of energy in an arctic ecosystem goes through a simple food chain from seaweeds to fish to seals to polar bears, then which of the following is true? a. The total energy content of the seaweeds is lower than that of the seals. b. The carnivores can provide more food for people than the herbivores can. c. There are fewer polar bears than there are fish. d. Seals are more numerous than fish. e. Polar bears can provide more food for people than seals can.

c. There are fewer polar bears than there are fish.

Autotrophs convert carbon dioxide into _____.

carbohydrates and other carbon compounds

Methanogens produce methane gas. What is this gas converted to in the atmosphere? a. Carbon dioxide and oxygen b. Carbon monoxide and ozone c. Ethanol and carbon dioxide d. Carbon dioxide and water

d. Carbon dioxide and water

What favors the production of peat? I. Presence of organic matter II. Anaerobic conditions III. Acidic conditions a. I and III only b. II and III only c. I and II only d. I, II and III

d. I, II and III

Subtraction of which of the following will convert gross primary productivity into net primary productivity? a. the energy fixed by photosynthesis b. all solar energy c. the energy used by heterotrophs in respiration d. the energy used by autotrophs in respiration e. the energy contained in the standing crop

d. the energy used by autotrophs in respiration

What is the fundamental difference between matter and energy? a. Matter is used in ecosystems; energy is not. b. Matter can be converted into energy; energy cannot be converted into matter. c. Energy can be converted into matter; matter cannot be converted into energy. d. Energy is cycled through ecosystems; matter is not. e. Matter is cycled through ecosystems; energy is not.

e. Matter is cycled through ecosystems; energy is not.

The main decomposers in an ecosystem are: a. fungi. b. plants. c. insects. d. prokaryotes. e. both A and D.

e. both A and D.

Which of the following are important biotic factors that can affect the structure and organization of biological communities? a. temperature, water b. light intensity, seasonality c. nutrient availability, soil pH d. precipitation, wind e. predation, competition

e. predation, competition

The energy released from carbon compounds by respiration is used in living organisms and converted to _____.

heat

What is lost from ecosystems?

heat

Most ecosystems rely on a supply of energy from _____.

sunlight

[SEE DIAGRAM] Why does the amount of CO2 fall between April and August? a. Seasonal decrease in the rate of photosynthesis in the northern hemisphere forests b. Seasonal increase in the amount of CO2 dissolved in the oceans c. Seasonal decrease in the rate of fossil fuel consumption d. Seasonal increase in the rate of photosynthesis in the northern hemisphere forests

​Seasonal increase in the rate of photosynthesis in the northern hemisphere forests