ECOLOGY Flashcards
(122 cards)
1
Q
what is ecology?
A
the study of the distribution and abundance of living organisms and their interactions with the environment.
2
Q
ecology is needed to understand evolution.
Give examples of the evolution of a Disease
A
1: Antibiotics are an effective treatment for bacterial infections because they reduce the population of the bacteria: this is an ecological effect (you will learn about predator prey dynamics and population growth later in this course). 2: Because there is variation in the bacterial population some of them are more resistant to the bacteria than others, and these are the ones that are more likely to survive (ecological effect: interaction between the bacteria and their environment). 3: These antibiotic-resistant bacteria have higher fitness, and therefore reproduce more, which means their population grows faster than the non resistant bacteria.
3
Q
Define ORGANISMAL
A
Organismal: How an organism’s structure, physiology and behaviour help them to survive and reproduce
4
Q
DEFINE POPULATION
A
Population: A group of individuals of the same species living in an area
5
Q
DEFINE COMMUNITY
A
Community: A group of populations of different species living in an area
6
Q
DEFINE ECOSYSTEM
A
Ecosystem: The community of organisms in an area and the physical factors with which those organisms interact
7
Q
DEFINE LANDSCAPE
A
Landscape: A mosaic of connected ecosystems
8
Q
DEFINE A BIOSPHERE
A
Biosphere: The global ecosystem – i.e. the sum of all the planet’s ecosystems and landscapes
9
Q
These are nested within each other: Global ecology -> landscape ecology -> ecosystem ecology -> community
A
YOU
CAN
DO
IT
ZULUBOY
10
Q
Interactions between organisms and the environment (ecology) determines spatial distribution
A
Both biotic and abiotic factors determine a species’ distribution.
11
Q
DEFINE BIOTIC FACTORS
A
Biotic factors are all other living organisms that are part of the individual’s environmentThese include: herbivory, predation, competition, parasitism, mutualism
12
Q
DEFINE ABIOTIC FACTORS
A
Abiotic factors are non-living factors (All chemical and physical factors)Temperature: Ectotherm vs Endotherm (Water in cells freezed in cold temp. while protein denature in high temperature)Water: Desert animals & plants (the ability to obtain and conserve water)Salinity: Affect osmoregulation (mangrove can excrete salt)Sunlight: PhotosynthesisRocks & soil:: Affect distribution of plants and thus animals that feed on them
13
Q
DIFFERENCE BETWEEN macroclimate and microclimate.
A
Macroclimate determines global patterns and microclimate determines how communities organise themselves at smaller scales
At the scale of the whole globe we have large differences in macroclimate: Sunlight intensity is highest at the equator and lowest at the poles. There is also seasonal variation in how long different parts of the globe experience daylight for.
14
Q
Solar radiation influences ocean and atmospheric circulation, which then influences precipitation: -There is more rainfall at the equator where there is convection and rising air currents-There is more rainfall on the east of South Africa where we have warm currents than in the west where we have cold currents.
A
At the scale of the whole globe we have large differences in macroclimate: Sunlight intensity is highest at the equator and lowest at the poles. There is also seasonal variation in how long different parts of the globe experience daylight for.
15
Q
and the lord said?
A
IT IS D-O-N-E
16
Q
difference between rising air and sinking air.
A
rising air (= convection = rain) vs sinking air (= subsidence = no rainfall)
17
Q
Microclimate is influenced by landscape features such as topography:
A
you can do it
18
Q
Mountains can also affect air movement, and therefore rainfall:
explain how this occurs.
A
The side of the mountain that the air rises on will have more rainfall than the side where the air is sinking. Mountains also affect how hot the environment is at different altitudes, and which side of the mountain is facing the sun (aspect).
Microclimate can also be influenced by other organisms (eg trees alter the way winds move, and the amount of sunlight and rainfall that reaches the ground).
19
Q
what is a biome?
A
A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. Biomes consist of ecosystems that share similar characteristics, and that are exposed to similar environmental conditions and disturbances.
20
Q
can an aquatic system have a biome?
A
YES
Within aquatic systems we also define different biomes. Some of these are in the ocean, and others in freshwater systems on land. Like terrestrial biomes these are affected by ocean circulation, largescale weather patterns, as well as topography (eg the intertidal zone).
21
Q
HOW MANY BIOMES DO WE RECOGNISE IN SOUTH AFRICA?
A
In South Africa we recognise 9 terrestrial biomes: Savanna, Grassland, Forest, Desert, Fynbos, Succulent Karroo, Nama-Karroo, Albany Thicket, and Indian Ocean Coastal Belt.
22
Q
WHY IS IT IMPORTANT TO UNDERSTAND PATTERNS OF population?
A
Understanding patterns of population increase and decrease is essential as it impacts many other aspects of ecology – including competition and predator-prey dynamics. One practical reason why we need to understand populations is to understand which species are at risk of extinction.
23
Q
Why would we be interested in population growth?
A
The patterns of population increase and decrease is essential as it impacts many other aspects of ecology – including competition and predator-prey dynamics. One practical reason why we need to understand populations is to understand which species are at risk of extinction.
24
Q
A population possess more characteristics the size
A
Density: number of individuals per unit area
25
A population possess more characteristics than just the size:
Dispersion: the pattern of spacing among individuals
26
A population possess more characteristics than just the size:
define demographics
Demographics: vital statistics of populations and how they change over time, mostly concern the addition and reduction of individuals, but also include age/sex structur
27
difference between population size and density.
Two populations can be of same size but different density. Size affects how viable the population is (as discussed above) but density affects things like the amount of resources each individual is able to get (competition) and disease transmissionLooking at density helps us to understand the size of population an ecosystem can sustain
28
what is dispersion and what are its 3 types?
Dispersion is the pattern of spacing among individuals; distribution of individualsIt can be clumped, uniform or random. Clumped – this occurs when there is a concentration of resources (like a water hole for elephants) or where organisms live in social groups Uniform – this occurs when there is strong territoriality – eg seabird colonies. Random – plants with seeds blown everywhere.
29
what is a Life Table?
An age-specific summary of the survival pattern of a population.
30
```
Survival is one of the factors that determine POPULATION SIZE<<<>>>
there are 3 survivorship curves-
namely
type I
Type II
Type III
```
Describe type I survivorship curve.
Type I: These curves have very low death rates during early & middle life, drops steeper getting to old age
(Large mammals like humans or elephants would be an example. They produce few offspring but have high parental care so these offspring are likely to survive)
31
describe type II survivorship curve.
Type II: This represents a constant death rate through life (equally likely to die at any time, random)
(rodents, invertebrates, lizards are good examples – they are prey items throughout their lives, and age doesn’t really affect survival)
32
describe type III survivorship curve.
Type III: These curves show high death rates for young, and then death rates decline if the organisms manage to stay alive
(examples would be organisms that produce lots of offspring but provide no care, e.g. long-lived plants, fishes, marine invertebrates)
33
There is high variety in reproductive tables: the patterns depend on age at sexual maturity and reproductive strategies. For example, humans and many plants delay reproduction until they are old and established and have acquired the resources they need to survive and reproduce effectively .
On the other hand, trees once they start to reproduce can produce many seeds each year for many years whereas Elephants: produce only one calf in every ~5 years
NELSON ZULU IS AS AMAZING AS HE IS.
BRUH
34
DEFINE Life History
A life history is the sequence of events related to survival and reproduction that occurs from birth through death
35
what are the 3 life history traits that are related to reproduction
Three important life history traits related to reproduction are: the timing of when organisms reproduce (what age, and how often), and how much investment they make in each offspring.
36
define semelparity
once-off reproduction, a large number of offspring
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Define iteroparity
repeated reproduction over the lifespan of the organism
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when is Semelparity an appropriate reproductive strategy?
semelparity is an appropriate reproductive strategy:
1: when environments are very variable, and it is not clear how long the adults will live (safer to invest all resources in reproduction and none in growth/survival).
2: when having large numbers of offspring can increase the survival of the offspring by overwhelming the predators (eg Bamboo and some fish species have semelparous reproduction)
39
When is Iteroparity an appropriate reproductive strategy?
Iteroparity is an appropriate strategy when there are dependable resources & intense competition for resources (eg zebra, elephant, humans)
40
how do we calculate the Change in population size?
Ultimately, the CHANGE in a population size is the number of BIRTHS plus the number of IMMIGRANTS minus the number of DEATHS minus the number of EMMIGRANTS.
Population change= (birth+immigration)--(deaths+emigration)
41
WHAT IS A CARRYING CAPACITY. Describe it in terms of (r) and population size.
carrying capacity – the maximum population size a particular environment can sustain.
This means that the value of r is not constant over time, but that it varies depending on resource availability, competition, disease, habitat availability (eg if all the nesting sites are full, then there is nowhere to have your babies).
As r approaches 0 the population approaches its “Carrying Capacity”
42
ASSUMPTIONS VERSUS REALITY
what are the assumptions made by the logistic and exponential models?
One of the key assumptions made by both the logistic and exponential growth model is that populations respond instantaneously. In reality there are often processes that results in lags/delays in the responsiveness of births and deaths to resource limitation.
The models assume a smooth decline when approaching carrying capacity, with birth rates adjusting to resource availability immediately
Reality: always overshoots when approached K – because animals can use their energy reserve
Population then drops and there is a delay in population growth before the increased offspring are born
43
There are two tyoes of organisms based in what processes control their demographics.
what are these 2 types?
r- selected
AND
K-selected
The names of these life history strategies comes from K (reached carrying capacity) and r (promote rmax)
44
What are r-selected species?
r-selected species are species that have very high intrinsic growth rates (high rmax values). These types of organisms are very good at recovering from disturbances, because they can rapidly increase in numbers. However, because of this, they can also rapidly overshoot their carrying capacity, so sometimes show very extreme population crashes also. This leads to much greater fluctuation in population numbers.
45
What are K-selected species?
In reality organisms are found on a continuum between extreme r-selection and extreme K-selection.
K-selected species are species that are able to persist and compete in situations of limited resources. They have adaptations to survive and reproduce with few resources (competitive ability and efficient use of resources). These tend to result in less rapid population increases (for example, K-selected species will often have fewer offspring, but invest more in the survival of each offspring) – this leads to more stable population fluctuations.
46
Define Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance.
Playing a critical role in maintaining the structure of an ecological community.
47
What is a METAPOPULATION?
A metapopulation is a group of populations that are separated by space but consist of the same species.
48
There can be imigration and emigration between metapopulations
There are different degrees in connectivity, and this can change over time
YOU CAN DO IT
KEEP GOING
MASTER THESE FC'S AND GO BACK TO YOUR NOTES.
49
Sometimes a population splits into different habitat patches
WHAT IS the SOURCE?
habitat patch that allows population to grow; sink: habitat patch of low quality that requires the support from source
50
Sometimes a population splits into different habitat patches
WHAT IS THE sink?
sink: habitat patch of low quality that requires support from the source
The sink population cannot support itself. It usually happens when the source population is saturated (to reduce competition)./././././
51
How can we identify the 3 main phases of human population growth?
1: low and stable population before the agricultural revolution
2: a steady increase after we were able to start producing our own food
3: an exponential increase after the industrial revolution
52
flip
you can do this boi chapter.
easy top
Agricultural revolution allows for greater control of food supply and dispersion of excess humans to other places
The result: a steady increase in people
53
Remember r (the reproductive number) is births-deaths.
Zero population growth occurs when r approaches zero.
But there are two ways to achieve zero population growth
What are these 2 ways?
: high birth rate and high death rate or low birth rate and low death rate.
54
as development proceeds in a country, it goes through what we call a “demographic transition”.
what is DEMOGRAPHIC TRANSITION?
The population moves from having a high birth rate and a high death rate, to having a low birth rate and a low death rate
55
HOW DOES THE DEMOGRAPHIC TRANSITION PROGRESS?
THERE ARE 4 STAGES
EXPLAIN WITH ALL THESE STAGES.
This diagram summarises how the demographic transition progresses:
Stage 1: When a society first started. Death rates and birth rates are high and roughly in balance. Population growth is typically very slow in this stage, because the society is constrained by the available food supply.
Stage 2: Developing country. Death rates drop quickly due to improvements in food supply and sanitation, which increase life expectancies and reduce disease. Birth rates remain high.
Stage 3: Birth rates fall due to various fertility factors such as access to contraception, increases in wages, urbanization, a reduction in subsistence agriculture, an increase in the status and education of women. Population growth begins to level off.
Stage 4: Birth rates may drop to well below replacement level as has happened in countries like Germany, Italy, and Japan, leading to a shrinking population.
Replacement: the level of fertility at which a population exactly replaces itself from one generation to the next
Regional population depends on which stage the country is in.
56
WHAT ARE AGE STRUCTURE PYRAMIDS?
Age structure pyramids are simple ways to reveal the differences in population characteristics
They show the relative number of individuals of each age in the population
57
how do you interpret an age structure pyramid?
A pyramid with large numbers at the bottom (many young people) is growing.
A pyramid with even numbers throughout reproductive years shows a stable population
A pyramid which is smaller at the bottom than the top is showing negative growth.
58
what is COMMUNITY ECOLOGY
remove this after you've mastered...
Community Ecology: The study of interactions between species in communities
59
What is an ECOLOGICAL NICHE?
Ecological niche: the role and functional position of an organism in an ecosystem. Each species has its role in the community.
Where it lives, what it eats, how and when it eats/reproduces
Most importantly – how it interacts with other species & the influence of the interactions in the function of the ecosystem
60
Inter-specific interactions
DEFINE MUTUALISM.
Mutualism: an interaction that benefits both species. For example plants provide sugars/energy to fungus, which then provides access to limiting nutrients in the soil to the plant.
61
inter-specific interactions
DEFINE PREDATION
Predation: One species (the predator) kills and eats the other (the prey). Herbivory is also a predation. As discussed in the population change lecture, this can be important because it has a positive effect on one organism and a negative effect on the other – can drive a Predator-prey evolutionary arms race.
62
Inter-specific interactions
DESCRIBE COMPETITON
Competition: when species compete for resources that limits their growth and survival. In this case the effect of each organism on the other is negative
63
what are the 4 inter-specific interactions?
competition(-/-)
Predation/herbivory(+/-)
Mutualism(+/+)
Commensalism(+/0)
64
inter-specific interactions
Describe Commensalism
Commensalism: Interactions that benefit one species but cause no effect (no harm or benefits) to the other.
65
define parasitism
Parasitism: one organism (the parasite) derives its nourishment (food) from another organism (host) and harms the host. Endoparasites live inside the other organism’s body (like hook worm) and ectoparasites live outside, like ticks
66
define symbiosis
Symbiosis is an over-arching term for interactions where species live in direct and intimate contact, including Mutualism, Commensalism, and Parasitism
67
what is epidemiology?
Epidemiology is the study of the patterns, causes, and effects of health and disease conditions in defined populations.
68
what is an epidemiological triangle?
An epidemiological triangle is a model of infectious disease causation (the way infectious diseases occur)
69
how many components does an epidemiological triangle have?
There are three/four components: External agent + susceptible host + environment (+ vector sometimes)
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epidemiological triangle
what is the agent?
Agent = the microorganism or pathogen that causes the disease. Generally, the agent must be present for disease to occur
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epidemiological triangle
what is the host???
Host = the organism infected by the agent that develops the disease
72
epidemiological triangle
| what is the environment?
Environment = external factors that allow for contact between agent and host and transmission of disease
73
no matter what, I need you to remember that
it is only in your mind telling you it is difficult, but trust me, IT IS NOT. So take a step back.
bottom line:::it is not difficult
74
epidemiological triangle
| what is the VECTOR?
Vector = an organism that transmits the infection by carrying the agents from one host to another
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Distinguishing between epidemiology and disease ecology
what is epidemiology?
Epidemiology focuses on the patterns in host populations, pathways, human environment (hygiene, habits), and how to control it
• Who is having the disease? Women? Men? Children? People from the city? People from rural areas?
• What is causing the disease? Which bacteria or virus?
• Where is the point of contact between host and agent? Water source? Food?
76
Distinguishing between epidemiology and disease ecology
Disease ecology is the study of the underlying principles that influence these spatio-temporal patterns of diseases
Disease ecologists look at interactions of behaviour and ecology between hosts and agents and how climatic, evolutionary and environmental factors could affect this interactions (Parasitism in community ecology)
• Do the pathogen and the host have a long term evolutionary relationship, or the interaction is recent and caused by environmental changes (pollution? temperature?)
• How do human activities change the frequencies and patterns of these interactions?
77
DEFINE ZOONOTIC DIESEASES.
A zoonotic disease is a disease/infection that is naturally transmitted between vertebrate animals and humans (WHO definition)
Zoonotic agents = bacteria, viruses or fungi originated from animals
78
BIRD FLU
Bird flu: virus moved from birds to human
79
ZIKA FEVER
Zika fever: virus transmitted by mosquitoes, but origin unknown (evidence from monkeys and rodents)
Rabies: virus from various mammal species to humans (most commonly dogs)
Smaller diseases: tick bite fever, diseases caused by parasites (hookworm, roundworms etc.)
80
Zoonotic diseases are everywhere and very close to us. They can be carried by your dogs
For example: Capnocytophaga canimorsus is a commensal bacterium in canine and feline species, but can cause illness in humans:
It results in organ failure including brain and heart
Consider stopping kissing your dogs/cats!
JUST A REMINDER
YOU CAN AND WILL DO IT
81
HOW CAN ZOONOTIC DISEASES BE TRANSMITTED.
Transmission of zoonotic diseases is similar to what’s shown in epidemiological triangle
It can be direct: rabies (from bites), bird flu (from dead birds)
Or indirect: malaria, dengue fever – in which case vectors transmit infectious diseases between humans (malaria) or from animals to humans
82
DISEASE POPULATION DYNAMICS
WHAT IS A NATURAL RESEVOIR?
The animal the disease originates from is also called a natural reservoir: the long-term host of a pathogen of an infectious disease.
i.e. the habitat in which the agent normally lives. Often the pathogen does not cause disease in the reservoir.
83
WHAT IS EID(EMERGING INFECTIOUS DISEASE)
An emerging infectious disease (EID) is an infectious disease whose incidence has increased in the past 20 years and could increase in the near future
84
Why are zoonotic diseases increasing?
LIST THE 5 REASONS WITHOUT DESCRIBING THEM
1: Land use change
2: Climate change
3: Bushmeat trade
4: Evolution
5: Globalisation and population growth
85
Why are zoonotic diseases increasing?
DESCRIBE LAND USE
1: Land use change:
By modifying the natural environment and displacing species from their habitats, humans can increase the abundance of reservoir hosts in human-dominated environments thereby increasing the risk for contact and disease transmission.
86
Why are zoonotic diseases increasing?
| DESCRIBE CLIMATE CHANGE
2: Climate change
As we discussed earlier - species have specific niches in the environment, including pathogens & vectors
The change in temperature, sea level, habitat due to climate change can influence the distribution & niche of the pathogens or increase the population size of the pathogens
For example the suitable habitat for the malaria-vector is predicted to increase with increasing temperatures
87
Why are zoonotic diseases increasing?
DESCRIBE BUSHMEAT TRADE
3: Bushmeat trade
Increasing demand for bushmeat and wild animal products, together with poor hygiene and health support can increase the risk of transmission between humans and pathogens
88
Why are zoonotic diseases increasing?
DESCRIBE EVOLUTION
4: Evolution
Pathogens have very short generation times and are continually evolving
Our activities create natural selection pressure for the pathogens
Humans share over 98 percent of our genome with chimpanzees and gorillas.
Human body is an ecosystem into which new pathogens can pathogens evolve
89
Why are zoonotic diseases increasing?
Globalisation and population growth
5: Globalisation and population growth
Pre-historic human populations were isolated. Epidemics were confined to small populations
As humans now dominate the biomass of the planet (remember nearly 8 million of us alive today), and travel constantly around the globe we become a better and better host for pathogens (remember, the success of a pathogen depends on its ability to spread from host to host)
90
Modelling the spread of disease
which model do we use?
SIR( Susceptible/Infected/Recovered)
91
To prevent disease outbreaks we need to understand the ecology of the reservoirs and vectors
Ecological niche modelling improves our understanding of epidemiologically relevant vector and parasite-reservoir distributions
you can do it
mageba
ndabezitha
92
what is Chagas Disease?
///CASE STUDY///
Chagas disease is a tropical parasitic disease found in large parts of south and central America
93
what an ecological niche?
We have already defined an ecological niche (reminder: “the specific set of biotic and abiotic resources that an organism uses in its environment”). One way for many organisms to co-exist is for each to use SLIGHTLY different types of resources
94
what is resource partitioning
If there are two species competing for the same resource, evolution by natural selection can result in one of the species using a different set of resources or similar resources at different times of the day or year.
95
Fundamental vs realised niche
Competition means that a species “realised niche” (the set of resources that they actually use) is smaller than its “fundamental niche”: the set of resources that they could use if they weren’t competing with other species.
96
Bacteria also compete with each other, sometimes inside our own body.
There are two species of bacteria that can found in our upper respiratory tract:
how do these bacteria work in our body???
Haemophilus influenzae and Streptococcus pneumoniae
Most of the time both of these species are harmless (they are opportunistic pathogens- it is a commensalism between us and the bacteria)
S. pneumoniae attack H. influenzae with hydrogen peroxide and stripping off the surface molecules H. influenzae needs for survival. When H. influenzae is attacked by S. pneumoniae, it signals our immune system to attack the S. pneumoniae.
Sometimes one wins, sometimes they coexist; sometimes things get nasty:
S. pneumoniae can produce a thick sugary armour when under attack by H. influenzae.
This can invade other tissues and cause serious diseases in us the human hosts, (we are casualties in war)
97
what is commensalism?
Commensalism is also a form of symbiosis where one species benefit from the interaction (commensal) and the other species are not impacted either positively or negatively (host).
One famous example of this are the interaction between remora/suckerfish and sharks (or other predatory fish). In this relationship, the remora attach themselves to the shark and benefits through picking up scraps from the prey of the shark. They also get a free uber ride and therefore do not need to spend energy on travel. Sharks on the other hand don’t have any real benefits from this and are also not in any way disadvantaged.
98
what are keystone species?
Keystone species are species that have strong control on community structure - not because of their biomas/numbers but because of their ecological niche and the way they affect ecosystem function
Beavers build dams: regulate water flow, create and maintain wetlands that support high biodiversity
Elephants break trees, maintain open savanna and provide food for smaller antelope species
99
what are disturbances?
Disturbances are rare/episodic events that can have big impacts on the population sizes and community structure: storms, fires, floods, droughts, human activities
Up until recently most ecological theory saw disturbances as extreme events that disrupted the natural functioning of ecosystems. However, more recently, ecologists have started to see disturbance as an integral part of ecosystem functioning that can maintain, or even promote diversity and ecosystem health
100
there are graphs
look at them
you are capable bruh. BELIEVE IN YOURSELF ALWAYS
TRUST ME, YOU DO NOT KNOW HOW MUCH YOU ARE CAPABLE.
101
after a disturbance, what is an ecological succession(Primary succession)?
In extreme cases (volcanic eruption), a disturbance can remove all existing vegetation.
The disturbed area will be colonized by pioneer species, which will be replaced gradually overtime when the ecosystem is slowly re-establishing itself.
Primary succession starts in lifeless area: no soil
102
WHAT IS SECONDARY SUCCESSION?
Secondary succession starts after a disturbance that leaves the soil intact.
Secondary succession is a very controversial topic: some people would argue that we should be managing ecosystems so that they can reach a “climax community state” and trying to exclude disturbances like fire.
103
WHAT IS THE ONLY SOURCE OF ENERGY INPUT TO AN ECOSYSTEM? explain.
solar energy.
1: Photosynthetic producers (PLANTS- YAY) convert solar energy to chemical energy (plants are only about 6% efficient at doing this, a lot of the light energy gets wasted – you will find out why in second year)
2: Plant biomass is therefore stored energy from the sun. This stored chemical energy is either CONSUMED by higher trophic levels, or DECOMPOSED back to water and carbon dioxide
3: Plants and animals and microbes use energy to keep alive, and they also release some energy as heat – so as the energy moves up the trophic levels it gets less and less.
4: So the energy comes in from the sun and goes out again as heat, but the chemical elements that are used to store and move the energy around the ecosystem are continuously recycled (carbon cycle, nitrogen cycle)
104
why are decomposers essential?
We can get unlimited energy from the sun but chemical elements have to be recycled
That is why decomposers are essential: they break down dead organisms or waste material into simple molecules which can be used by organisms again
105
is a dung beetle a decomposer?
No, they are scavengers (detritivores): animals that feed on dead organic material (dead plant/animal remains/ or waste)
The dung beetles still rely on microbes and fungi to do the job of breaking the chemical bonds between organic molecules and turning them back into inorganic molecules.
But Dung beetles do facilitate decomposition – they have an important role to play
106
Nutrient cycling involves both biotic & abiotic components: “bio-geo-chemical”
how do nutrients move through different reservoirs?
The nutrients move through different reservoirs (plants, rocks, air, ocean soil). These differ in two main ways:
1: are the nutrients in an organic form or an inorganic form?
2: are the materials available for uptake by organisms?
107
how can respiration occur?
Respiration can happen in many ways
– decomposition by microbes,
- respiration by living organisms’ metabolisms (we respire CO2 all day),
- burning of wildfires which releases energy from the biomass and returns the CO2 to the atmosphere
- Burning of fossil fuels by people (the coal and oil that we burn are just plants that photosynthesized and stored the sun’s energy millions of years ago. Now we are using the stored energy and respiring the CO2 back to the atmosphere ).
108
Nitrogen is a nutrient that is used as a building block (muscles, tissue etc – it is important in amino acids).
how is it cycled?
Specialised organisms have to fix the nitrogen and turn it into an inorganic form that can be used by plants (nitrogen fixers). Legumes like Peas and Beans are Nitrogen Fixers.
Nitrogen enters nutrient cycle by nitrogen fixation and goes back to the air via ammonification in decomposition
109
Phosphorus is also important for life because it is part of ATP (adenosine triphosphate) and other energy-storing molecules
how is it Recycled How do plants get Phosphorus?
Plants get phosphorus from weathering of the rock. Like with nitrogen, this is a scarce nutrient, especially in places with old rocks which have little phosphorus. It can often be the factor that limits plant growth (and we also add it as fertiliser when we want to increase plant growth)
Once phosphorus is lost to a system through leaching it takes a long time to come back – it has to cycle through the whole earth system again and come back as rock
110
Slide 15
Altering nutrient cycling: Agriculture
- When we cut down natural vegetation we are removing a stock of carbon and energy and releasing it back to the atmosphere.
- When we plow up the soil we speed up decomposition and release carbon dioxide and nitrogen to the atmosphere.
- Because we harvest our crops, we take away their nutrients, and the soils become poor and cant support plant growth
- So we add fertiliser (that we sometimes bring from elsewhere and sometimes make using industrial processes).
- This fertiliser alters growth of the crops, but also spreads into natural ecosystems and alters their growth and food web dynamics.
Which cycles are affected and how:
Carbon cycle: less carbon stored in the vegetation and soil means more in the atmosphere causing global warming
Nitrogen cycle: much of the fertiliser we add to our croplands ends up in the rivers and oceans causing pollution, or in the air as greenhouse gases that also damages our health
Phosphorus cycle: because we add TOO MUCH phosphorus to our croplands this also ends up in the rivers and the oceans causing pollution and dead zones in the sea
Water cycle: this is more complex: when we irrigate and change the land cover we can alter rainfall patterns and soil water recharge. It depends on circumstances.
111
Altering nutrient cycling: Fossil fuels
- The coal, oil, and gas that we use to provide energy to fuel our economies and lifestyles used to be a STOCK: stored deep underground.
- The carbon-based molecules in these fossil fuels did come from the atmosphere originally – 300 million years ago trees grew and photosynthesised and captured carbon and grew: then this carbon became fossilised
- So when we burn it, we are putting carbon back into the atmosphere that has been sequestered safely underground for millions and millions of years.
Which cycles are affected and how
Carbon cycle: suddenly we have more CO2 in the atmosphere than we have had for at least 30 million years (life as we know it, and humans, have never lived with so much CO2 in the atmosphere).
Nitrogen cycle: burning fossil fuels provides another way to “fix” nitrogen – so we have doubled the amount of nitrogen cycling through our ecosystems also.
Sulphur cycle: the fossil fuels also have sulphur in them
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Altering nutrient cycling: Water pollution
When we fertilise our croplands we don’t do it efficiently, and a lot (sometimes up to 60%) of the nutrients get lost back into the atmosphere, or washed into the rivers.
Eutrophication is an excess amount of nutrients in aquatic systems.
Why are more nutrients bad in aquatic systems?
-> sometimes extra nutrients cause the growth of Cyanobacteria which produce cyanotoxins, and result in contaminated water and seafood
Paralytic Shellfish Poisoning: disrupt normal nerve functions, nausea, musle incoordination (Death 2-24 hours)
Diarrhetic Shellfish Poisoning: diarrhoea, nausea, vomiting, stomach ache and shivering (<4 hours, relatively mild)
- Ecological management of coastal waters is required to control these health problems
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Altering nutrient cycling: Air pollution
Burning of wood and fossil fuels releases sulphur dioxide and nitrogen oxides. These react with water and form sulfuric and nitric acid
This means that when it rains the rain is acidic: Acid rain, snow, sleet or fog.
what are the consequences of Acid Rain?
Consequences of Acid rain:
- Lowers pH of streams and lakes,
- Affects soil chemistry and nutrient availability (in acid soils it is hard for plants to take up nutrients)
- damages plants
- In Europe the rain was so acidic it was eating away at all their historical buildings – they put in strong pollution laws and things have improved since then.
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Altering nutrient cycling: Air pollution
Pollutants from fossil fuel burning and agriculture can also make us sick.
Nitrogen dioxide (NO2) and other gases result in respiratory diseases and eye, nose, and skin irritation. This is a big problem in Johannesburg and Mpumalanga in the winter.
What are some human health consequences of air pollution?
Some of the human health consequences: respiratory disease, pulmonary disorders and heart disease (premature age blood vessels, rapid build up of calcium in coronary artery; accelerates atherosclerosis)
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Altering nutrient cycling: climate change
Air pollution causes climate change. Climate change is a change in the statistical distribution of weather patterns that lasts for an extended period of time
Can be natural: solar radiation, plate tectonics, volcanic eruptions -> little ice age
Altering nutrient cycling: climate change
Air pollution causes climate change. Climate change is a change in the statistical distribution of weather patterns that lasts for an extended period of time
Can be natural: solar radiation, plate tectonics, volcanic eruptions -> little ice age
It is called anthropogenic climate change when it is caused by human activities
It is called anthropogenic climate change when it is caused by human activities
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what is SPECIES DIVERSITY.
Species diversity: this is what most people think about when they use the term “biodiversity”: the number of different species in an area. But even this is quite complicated to think about spatially: for example would two landscapes each with 3 unique species be more or less diverse than one landscape with 10 unique species?
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WHAT IS FUCNTIONAL DIVERSITY?
Functional diversity: this is a concept used to account for the fact that some species are more similar than others – so having 3 similar species in a system might be less diverse than having two different ones. To quantify functional diversity you have to think about how species function, and try to quantify “functional types” of species (groups of species that act in the same way
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ECOSYSTEM DIVERSITY DEFINITION?
Ecosystem diversity: At bigger scales people talk about ecosystem and structural diversity: here they try to quantity how different two habitats/landscapes are from each other
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what is Habitat fragmentation?
Habitat fragmentation is a slightly different thing from habitat loss, although it results from habitat loss.
Fragmentation is the division of large, continuous habitats into a greater number of smaller patches of lower total area.
This results in
- Isolated populations
- Lots of habitat edges and not much core habitat
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how can Overexploitation devastate biodiversity?
Overexploitation: Human harvesting wild organisms at rates that the population cannot replenish itself
We have always been part of the food web and hunted/foraged on other organisms for food/medicine and shelter.
However, with improved technology we are now able to do this much more efficiently – to the point that our prey population dynamics are affected and they can go extinct
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what is a Transboundary Protected Area (TBPA)?
A transboundary protected area (TBPA) is a protected area that spans boundaries of more than one country or sub-national entity. There are 9 in SA.
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WHAT IS SUSTAINABLE DEVELOPMENT?
Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
The aim is to improve human conditions while conserving biodiversity.
It requires inputs from all disciplines: life science, social science, humanity, economic development.
It also requires good laws and policing of these laws.
