19: Ecosystems Flashcards
1
Q
What is the definition of habitat?
A
The habitat is the place where organisms live.
2
Q
What is ecology?
A
Ecology is the study of the inter-relationships between organisms and that between organisms and their envrionment.
3
Q
What are all levels of organisation in ecological studies ranked from low to high?
A
Species, population, community, ecosystem, biome, biosphere
4
Q
What does the term “species” refer to in ecological studies?
A
Species is the lowest level of classifying organisms. It consists of organisms that can interbreed and produce fertile offspring.
5
Q
What does the term “population” refer to in ecological studies?
A
Population refers to a group of organisms of the same species living in the same habitat.
6
Q
What does the term “community” refer to in ecological studies?
A
Community refers to all the populations of different species living in the same habitat.
7
Q
What does the term “ecosystem” refer to in ecological studies?
A
An ecosystem is a natural unit of the living components (the organisms in a community) and the non-living components (the physical envrionment). These components interact to form a self-supporting, stable, yet dynamic syetem in a particular area.
8
Q
What does the term “biome” refer to in ecological studies?
A
A biome is a complex of communities that occupies a large geographical area. It is characterised by a dominant type of plant, which is determined by the climatic comditions.
9
Q
What does the term “biosphere” refer to in ecological studies?
A
Biosphere refers to the entire space on the Earth’s surface where organisms exist. It consists of the land, the water and the lower part of the atmosphere.
10
Q
What is an example of a biome and its locations?
A
The savanna biome is located in Africa, India, the northern part of Australia and the middle part of south America.
11
Q
At which ecological level should we study how the body features of the individuals of a species adapt to ther envrionment?
A
At the species level
12
Q
At which ecological level should we study how environmental factors affect the number of a certain species?
A
At the population level
13
Q
At which ecological level should we study the interaction among different species in a habitat?
A
At the community level
14
Q
At which ecological level should we study the cycling of materials between organisms and their environment?
A
At the ecosystem level
15
Q
At which ecological level should we study the impact of human activity on global ecological processes like global warming?
A
At the biosphere level
16
Q
What are the features that are essential to keep the ecosystem self-supporting, stable, and dynamic?
A
Cycling of materials, interactions of organisms with one another and with the envrionment, and energy input
17
Q
How does the cycling of materials maintain the properties of an ecosystem?
A
Useful elements like carbon and nitrogen inside organisms are not lost from the ecosystem. Instead, they are cycled through the ecosystem when the organisms carry out photosynthesis, respiration, excretion, egestion or when they die. Thus, an ecosystem does not require the supply of extra materials, explaining why it is stable and self-supporting.
18
Q
How does feeding maintain the dynamic properties of the ecosystem?
A
Feeding is a form of material cycling and interaction of organisms with one another and with the envrionment, making an ecosystem dynamic. In feeding, materials are transferred from one organism to the other in the form of food.
Inorganic materials in the envionment may be absorbed by the organisms and may be converted to organic matter through autotrophic nutrition. Materials may be released back to the envrionment through respiration, excretion and decomposition of dead organic matter.
19
Q
How does competition maintain the dynamic properties of the ecosystem?
A
Some species may compete for common resources, such as living space, which is a kind of interaction of organisms with one another, making the ecosystem dynamic.
20
Q
How does the adaptation of organisms maintain the dynamic properties of the ecosystem?
A
Organisms shows different adaptations in order to live in specific envrionments. On the other hand, organisms also affect their physical environment. For example, they may take up substances and release waste into the environment. They may also modify their physical environment by speeding up erosion or stabilising the substratum.
21
Q
Why is the sun required to sustain an ecosystem?
A
Energy in an ecosystem cannot be cycled. As the survival of organisms require a continuous supply of energy, there must be a continuous input of energy into the ecosystem, which usually comes from the sun.
22
Q
How is energy transferred from one organism to another and how is it lost?
A
Energy is transferred from one organism to another in the form of food and lost as heat.
23
Q
What are the two components making up an ecosystem?
A
The abiotic factors and the biotic community
24
Q
How does temperature affect the distribution and behaviour of organisms?
A
Metabolic reactions in the cells are catalysed by enzymes, which only work best within a narrow range of temperatures.
25
How do homoiotherms and poikilotherms respond to a change in environmental temperature?
**Homoiotherms** retain a **steady body temperature** while **poikilotherms**' body temperature **fluctuates with the envionmental temperature**.
26
What are some adaptations by animals living in warm areas?
The evaporation of water from sweat, and **panting** in dogs which evaporates water from saliva
27
What are some adaptations by animals living in cold areas?
**hibernation**; thick layer of **subcutaneous fat** under the skin acting as insulators; penguins huddle together to reduce the collective **surface-area-to-volume-ratio**
28
Name 4 types of bacteria classified according to living temperature.
from low to high: psychrophiles, mesophiles, thermophiles, hyperthermophiles
29
How does light affect plants?
Light intensity mainly affects the **rate of photosynthesis** in plants, while the **day length** affects the **flowering** of plants
30
What is the difference between diurnal animals and nocturnal animals?
diurnal animals are active during the day and rest at night, while nocturnal animals are active at night.
31
What are the adaptations of organisms in habitats with limited water supply?
They develop special mechanisms to **retain water** in their body and **reduce water loss**, such as spiny leavs and waxy skin on cacti.
32
How do wind speed and water current affect the distribution of organisms?
In terrestrial ecosystems, strong wind may blow the soil away, making the soil not suitable for the growth of **large plant species**.
In aquatic ecosystems, strong winds may generate **strong waves** that wash immobile or slow-moving animals away.
33
What are the adaptations of organisms in windy habitats or fast-flowing water?
They develop body structures to **hold** themselves **firmly onto the substratum**. In aquatic habitats, they may have a **streamlined body** to reduce resistance while moving in water.
34
What are 2 other abiotic factors water current can influence?
Oxygen level: the higher the speed of water current, the **higher** the oxygen level in the water.
Particle size of substratum: the higher the speed of water current, the **larger** the particle size since smaller particles are washed away.
35
Name 3 abiotic factors influencing oxygen level in aquatic habitats.
Temperature, water current, organic matter
36
How does temperature affect the oxygen level in aquatic habitats?
The higher the temperature, the **lower** the oxygen level, since the solubility of oxygen in water **decreases** as temperature increases.
37
How does the speed of water current affect the oxygen level in aquatic habitats?
The higher the speed of the current, the **higher** the oxygen level, since splashes increase the **contact area** of water with oxygen.
38
How does the amount of organic matter affect the oxygen level in aquatic habitats?
The presence of organic matter **lowers** the oxygen level, since the decomposition of organic matter uses oxygen.
39
What is salinity and its significance?
Salinity refers to the **concentration** of **dissolved salts and ions** in water. It directly determines the **water potential** and hence the availability of water and minerals to organisms.
40
Where does salinity have a large fluctuation daily?
In the intertidal zone
41
What is the meaning of substratum?
Substratum refers to the material that the organisms are growing on or attaching to. It varies from bare rock to soil of different **particle sizes**, including any **stable surface** provided by organisms like tree trunks and coral reefs.
42
What are the characteristics of soil with small particles?
The **air spaces** among the particles are small and the concentration of oxygen in the soil is lower. The soil is easily flooded with water (ie becomes **water-logged**).
43
How is humus formed?
Humus is formed from the **decomposition of organic matter** by microorganisms in soil.
44
What are the characteristics of humus?
It is the **major source of nutrients** in soil for plant growth. It can hold a **large amount of moisture**, therefore increasing the soil's capacity to withstand drought conditions.
45
How are abiotic factors altered by plant layers in a woodland?
**Light intensity** and **temperature** differ at different layers of a woodland. The **canopy layer** forms a **shelter** against strong wind and heavy rain. This helps **prevent soil erosion** and **reduce runoff**.
46
How are abiotic factors altered by tree roots and humus in a woodland?
The tree roots are deep. The extensive root system **holds the soil particles** together. This helps prevent **soil erosion** and **reduce runoff**. A thick layer of humus on the ground layer maintains fertility of the soil.
47
Name two major types of coastal ecosystems.
rocky shores and mangroves
48
What are the characteristics of the substratum of rocky shores?
They have a **hard substratum** since the habitat is exposed to **strong waves**.
49
Name 5 zones a rocky shore can be divded into vertically.
from high to low: splash zone, high tide zone, mid tide zone, low tide zone, subtidal zone
50
How is zonation seen in rocky shores?
Specific groups of organisms are found in each zone.
51
What are the adaptations of organisms living in rocky shores?
Many organisms develop ways to **attach** themselves firmly to the rocks, such as muscular foot. Most of them also have a **hard shell** for protection and to prevent them from drying up. Some organidmd stay away from strong waves by **hiding themselves in rock crevices**.
52
What are the characteristics of mangroves?
Most of them are located in **sheltered bays**, which are subject to **tidal actions**. There is a continuous exchange of waster from the river and the sea. Therefore, the **salinity** of the mud **fluctuates** throughout the day.
Organic matter can easily **accumulate** in the soft mud and the **oxygen level** is low.
53
What are the adaptations of mangroves?
Specialised roots: Mangroves develop roots that are raised **above the mud** to obtain oxygen from the air, such as **knee joints** which bend upwards and **pneumatophores** which stick up.
Salt secretion: some mangrove trees can **excrete excess salt** through their leaves.
54
What is the significance of specialised roots of mangrove trees?
The specialised roots facilitate the **absorption of oxygen** of the mangrove tree, which in turn facilitates the absorption of minerals and nutrients of the tree.
55
What is the significance of salt excretion of mangrove trees?
The excretion of salt ensures that the **water potential** of the tree is kept high enough, therefore ensuring that the tree has enough water content.
56
How do mangroves attract animals?
The large amount of **organic matter** that accumulates in the substratum of mangroves **provides a food soruce** for a diversity of animals. Their distribution in the mud is affected by the **oxygen level** and **particle size** of the substratum.
57
What are the differences between the upper course and the lower course of freshwater ecosystems?
The upper course has a **faster water flow**, therefore it has a **higher oxygen level**. The particles of substratum are **larger** since the smaller ones are washed away.
The lower course has a **slower water flow**, therefore it has a **lower oxygen level**. The particles of substratum are **smaller**.
58
What are the adaptations of organisms living in freshwater ecosystems?
Some of them are **flattened in shape** to reduce the resistance when swimming. They may also **hide in rocks** or develop **suckers** to prevent being washed away by the strong water currents.
59
Name 5 functions of plants in freshwater ecosystems.
Provide food, regulate water temperature, purify water, reduce the risk of flooding and reduce erosion.
60
Why are grasslands dominated by short grass species?
The growth of larger plants is limited due to the **strong winds**.
61
What is the difference between habitat and niche?
A habitat is the **place** where an oranism lives, which provides the conditions the organism needs to survive. A niche is the **role** that an organism plays in its envrionment. It refers to the **way of life** of an organism in its natural habitat.
62
What is the relationship between habitat and niche?
In a habitat, each species occupies a specific niche.
63
What are factors that determine the niche of an organism?
Temperature range in which they live, types of food they eat, and the space they occupy.
64
What are the factors that determine species diversity?
Species richness and the relative abundance of different species.
65
How is the species richness obtained?
The species richness of a community is determined by summing up the numbers of all species.
66
What are dominant species?
Dominant species are the ones that exert a **strong influence** on the composition and diversity of the community. In terrestrial ecosystems, they are usually the **most common type of plants**, since the types of animals in a community greatly depends on the types of plants living in the same area.
67
What is predation?
Predation is the interaction between two species in which one species **hunts, captures, and kills** the other for food. The organism that eats the other is the **predator** while the one being eaten is the **prey**.
68
How are the two organisms affected in predation?
The predator gains benefit while the prey is harmed.
69
Describe the predator-prey cycle.
1. The prey has plenty of food; its **birth rate** is **more** than its **death rate** and its population **increases**.
2. An increase in prey number means more food is available for predators. Their **birth rate** is **more** than their **death rate** and its population **increases**.
3. More prey are eaten. The **death rate exceeds the birth rate**, and the population **decreases**.
4. The food supply for predators are limited, their **birth rate decreases**, so the predator population **decreases**.
5. Since there are less predators, the prey's **birth rate exeeds the death rate**, and their population **increases**.
70
What are the characteristics of the predator-prey graph?
There is usually a **cyclic fluctuation**. The change in the **population of the predator** is always **lagging behind** that of the prey. The maximum number of prey is higher than that of the predator.
71
Why is the maximum number of prey is higher than that of the predator?
Due to **inefficient energy transfer** between trophic levels, one predator feeds on a **large number of prey** in order to sustain its life.
72
Name 4 techniques prey escapes from predators.
Camouflaging; secretion of toxins; mimicry; startling the predator
73
What is competition?
Competition refers to fighting for some common needs like food, space, shelter, sunlight, and mates.
74
How are organisms affected in competition?
All organisms involved in competition are **harmed**.
75
Name two types of competition.
Interspecific competition, intraspecific competition
76
What is the difference between interspecific competition and intraspecific competition?
Interspecifc competition refers to competition **among different species**, and the **stronger competitor** would be able to occupy a more favourable area within the habitat.
Intraspecific comeptition refers to comeptition **within the same species**. It is usually **more intense** than interspecific competition since individuals of the same species have the **same niche** and hence the **same needs**.
77
How are organisms affected in commensalism?
One **gains beneifts** while the other is **not affected**.
78
How are organisms affected in mutualism?
Two organisms **both gain benefits**.
79
How is mutualism shown in lichens?
Lichens consist of **algae and fungi** living together. The algae **make food** by photosynthesis for both organisms while fungi form a sponge-like body that holds water and **provides protection and anchorage** for both organisms. Together, they can grow on places where neither could survive alone, like on tree trunks and barren rocks.
80
How are organisms affected in parasitism?
One organism lives on or inside other organisms, gaining **benefit** from them but causing them **harm**. The organism benefitting is the **parasite** while the one being harmed is the **host**.
81
What is ecological succession?
The **variety of species** of a community **changes gradually** as a result of interactions between organisms and the physical envrionment. This series of changes in the composition of a community over a period of time is called **ecological succession**.
82
What are the steps of ecological succession?
Organisms **modify their envrionment** in ways that allow **other species** to come in and **replace** them. The process repeats itself and the **species diversity progressively increases** as more and more species appear in the community. Species diversity reaches a **maximum** where a **climax community** is reached.
83
Name two types of ecological succession.
primary succession and secondary succession
84
What is the difference between primary and secondary succession?
Primary succession starts with the **colonisation of a barren area** where there were no soil or organisms before, while secondary succession takes place in areas that **once supported life** but are now barren due to a **major disturbance**.
85
What are the events happening between years 0-15 of primary succession?
**Barren rocks** are exposed. As a result of **weathering**, the rocks are **broken up** into smaller particles. **Lichen spores** are brought to the rocks by wind. The lichens grow and form the **pioneer community**. Their dead bodies are **decomposed** to become **organic matter**. The small rock particles and the organic matter gradually form the soil.
86
What are the events happening between years 15-35 of primary succession?
Mosses, ferns, and grass start to grow in the soil. They become established over most part of the rocks and become the **dominant species**. They provide food and shelter for plant-eating animals.
87
Why are lichens often the pioneer community in primary succession?
They are able to grow in adverse, dry conditions.
88
What are the events happening between years 35-80 of primary succession?
Dead, decaying plants and animals, as well as animal waste form **humus** which further **enriches the soil**. The soil becomes thick enough for the growth of **shrubs**. The shrubs grow over the mosses, and they become the dominant species. More animals are attracted to the habitat because there are more food and shelter.
89
What are the events happening after year 80 of primary succession?
The soil becomes thick and **rich in nutrients**. It can support the growth of **trees** which grow over the shrubs, becoming the dominant species. The habitat turns into a **woodland** that attracts inreasing number of animals. A **climax community** is reached.
90
What are the characteristics of a climax community?
It has the **largest variety of species**. A **maximum biomass** and the **greatest organism interactions** are maintained.
The **energy input** to the ecosystem is balanced by the **energy consumed**.
If it is **disturbed** by some external force, it will **redevelop** until it attains stability through secondary succession.
91
What are the organisms making up the pioneer community in secondary succession?
Grasses and ferns. Lichens are not needed as soil is already present.
92
How is the time needed to reach climax community different in primary succession and secondary succession?
Secondary succession **develops more quickly** than primary succession. This is because **seeds, roots, and vegetative organs** of plants may still survive in the soil. They can grow and develop into plants rapidly once the conditions become favourable.
93
What is the source of energy in an ecosystem?
The sun
94
How is energy transferred in an ecosystem?
Energy flows in the form of **food** in an ecosystem.
95
Why is a continual input of energy needed for an ecosystem?
Energy is **lost** from the organisms through different processes.
96
What are the characteristics of producers?
They can make thier own food and are **autotrophs**. Most of them are **photosynthetic**; they capture light energy and convert it into chemical energy stored in organic compounds.
97
What are the characteristics of consumers?
They depend on other organisms for food and are **hetertrophs**. They **feed on other organisms** to transfer energy along food chains in the form of **food**.
98
What is the food chain formed by a producer and 3 consumers?
producer -> primary consumer -> secondary consumer -> tertiary consumer
99
What is the difference between a food chain and a food web?
A food chain shows the sequence of organisms in a **particular feeding relationship**, while a food web shows **all the possible relationships** among selected organisms in an ecosystem.
100
What is trophic level?
A trophic level is a level in a food chain. It is the **feeding level** of the organism depending on what it feeds on, and by what organism it is eaten.
101
Name 4 ways in which energy is lost when it is transferred from the lower trophic level to the higher trophic level.
Uneaten materials, undigested and egested materials, excretory products, and as heat during respiration.
102
Explain two ways of energy loss between trophic levels when a rabbit feeds on grass.
When the rabbit feeds on the grass, some energy is lost when parts of the grass is **not eaten** by the rabbit.
When the rabbit feeds on the grass, some energy is lost when some parts of the grass are **undigested, unabsorbed and egested** by the rabbit.
103
Explain two ways of energy loss within the higher trophic level when a rabbit feeds on grass.
When the rabbit feeds on the grass, some energy is lost in **excretory products**.
When the rabbit feeds on the grass, some energy is lost as **heat released from respiration** of the rabbit.
104
Why is the number of trophic levels limited?
Due to a great loss of energy along a food chain, the number of trophic levels in a food chain is limited. With fewer trophic levels, less energy is lost and the **shorter food chain** can support **more consumers** than a longer food chain.
105
What is decomposition?
Decomposition is the process in which decomposers secrete **digestive enzymes** outside their bodies to **break down dead organic matter**.
106
What is the significance of decomposers in an ecosystem?
They absorb **inorganic nutrients** released from the breakdown of dead organic matter.
They carry out **respiration** to release **carbon dioxide** back to the atmosphere. Therefore, they are important in **material cycling** in an ecosystem.
107
What is a pyramid of numbers?
The pyramid of numbers is a **bar diagram** showing the **number** of organisms at each trophic level.
108
Why does the sizes of the bars of a pyramid of numbers decrease up the pyramid?
**Less energy** it available to organisms at **higher trophic levels**.
Also, a predator is usually **larger in body size** than its prey, and hence **requires more energy** to maintain its life. Therefore, the number of organisms that can be supported at a higher trophic level is usually smaller.
109
Explain one situation where the pyramid of numbers is inverted.
Since the **size** of the individual is not considered, a producer that is large in size can support many primary consumers (eg oak tree and caterpillars).
110
What is the definition of biomass and its unit?
Biomass is the **total dry mass** of organisms at each trophic level in a **given unit area** at a **particular point of time**. It is usually measured in g m-2.
111
Why can a pyramid of biomass reflect the energy flow between trophic levels?
The amount of **energy** stored in an organism is usually proportional to the **amount of living material** in its body. Therefore, changes in the amount of energy flowing through trophic levels can be represented by changes in the total biomass of organisms at different trophic levels.
112
Explain one situation where the pyramid of biomass is inverted.
Since the **lifespan** of organisms are not considered, the pyramid becomes inverted when organisms at a **lower trophic level** have a much higher reproduction rate and shorter lifespan (**high turnover rate**) (eg phytoplankton and zooplankton).
113
List two limitations of ecological pyramids.
The energy flow to **decomposers** is not considered.
The **trophic level** of an organism, especially carnivores, may **vary** with the type of food eaten. Some organisms may also **change their diet** as they grow. Thus it is often difficult to assign them the correct trophic level.
114
How is carbon transferred from a lower trophic level to a higher trophic level?
Carbon in producers, in the form of **organic matter**, is transferred to consumers at higher trophic levels by **feeding**.
115
How is carbon transferred from trophic levels to decomposers?
Organic matter in dead bodies or waste material or organisms is used as **food** by decomposers, which are **saprophytes**.
116
How is carbon returned to the atmosphere and the oceans from organisms?
Carbon in organic matter is converted into **carbon dioxide** and released into the atmosphere and ocean during **respiration** of all organisms and **decomposition** by decomposers.
117
How is carbon returned to the atmosphere and the oceans from organisms through fossil fuels?
The dead bodies of organisms may become **fossil fuels** if they are quickly covered by sedients and are buried under high pressure for millions of years. During **combustion** of fossil fuels, the carbon inside the fuels is released as **carbon dioxide**.
118
How is carbon returned to the atmosphere and the oceans from organisms through volcanic eruptions?
The **carbonate skeletons** of certain marine organisms may deposit into the oceas bed and turn into **limestone**. When the carbonates in the limestone react with acids in water, or when they are heated under high pressure during **volcanic eruptions**, **carbon dioxide** is released.
119
How is carbon removed from the atmosphere and oceans?
Carbon dioxide in the atmosphere and oceans is returned to the bodies of producers when the producers carry out **photosynthesis**. The carbon eventually **enters the food chain** again as organic matter.
120
Under what condition is the carbon cycle kept balanced?
The carbon cycle is kept balanced if the **rate of addition** of carbon dioxide to the atmosphere and oceans is equal to the **rate of removal** of carbon dioxide.
121
How is nitrogen transferred from a lower trophic level to a higher trophic level?
Nitrogen, in the form of organic matter, is transferred from producers to consumers at different trophic levels by **feeding**.
122
How are ammonium compounds added to the soil?
Through decomposition, decomposers break down **organic waste** and the dead bodies of producers and consumers. The nitrogen in these materials is converted to **ammonium compounds** (also called **ammonification**).
123
How are ammonium compounds in the soil converted to nitrates?
They are turned into **nitrites** by **nitrifying bacteria**, which are then turned into **nitrates** also by **nitrifying bacteria**. The process is called **nitrification**.
124
How is nitrogen in soil air converted to ammounium compounds?
Free-living **nitrogen fixing bacteria** in the soil can convert nitrogen in soil air into ammounium compounds through a process called **nitrogen fixation**.
125
How are the ammounium compounds in nitrogen fixing bacteria converted to nitrates?
When nitrogen fixing bacteria die, they are **decomposed** by decomposers. The ammounium compounds inside the bacteria are released into the soil and converted to **nitrates** by **nitrification**.
126
Where are nitrogen fixing bacteria commonly found and why?
Inside the **root nodules** of **leguminous plants**, since the ammounium compounds can be taken up by the plant for growth.
127
What is the ecological relationship between nitrogen fixing bacteria in root nodules and the plant they grow on?
Mutualism: the plant benefits from uptaking ammonium compounds, which promote its growth. Meanwhile, the plants provides the bacteria with food and shelter.
128
How can nitrogen in air be converted to nitrates in the soil without the action of microorganisms?
**Lightning** turns nitrogen in the atmosphere into **nitrogen oxides**, which is then dissolved in rainwater to form **nitrates** in the soil.
129
How is nitrogen removed from the soil with the action of microorganisms?
In **poorly aerated soil**, **denitrifying bacteria** change nitrates in the soil into nitrogen gas through a process called **denitrification**. The nitrogen gas then diffuses into the atmosphere.
130
How is nitrogen removed from the soil without the action of microorganisms?
The nitrates formed as a result of nitrification and lightning are eventually **taken up by producers** for the synthesis of proteins, nucleic acids and other nitrogen containing organic compounds.
131
Under what condition is the nitrogen cycle kept balanced?
The nitrogen cycle is kept balanced if the **rate of addition** of nitrogen-containing compounds to the soil is equal to the **rate of removal** of these comopunds from the soil.
132
List 4 impacts human activities have on ecosystems.
Habitat destruction, overexploitation of resources, pollution, and global warming
