Ecology Flashcards
Population ecology:
- the study of population in relation to their
environment. - How biotic and abiotic factors influence the abundance,
dispersion and age structure of populations.
population
a group of individuals of a single species living in the same area that can interbreed and produce fertile offspring
Density:
the number of individuals (of a pop) per unit area or volume
Changes as individuals are added or removed from a population via births and deaths (natality and mortality) and emigration and immigration
Dispersion:
pattern of spacing among individuals within the boundaries of the pop.
Clumped:
- Individuals aggregate in patches because the resources are
rife there and they are better able to survive - May also be due to mating behaviour
- Where they can breed effectively
- Increases the predation or defence of the group
Uniform:
- Evenly spaced pattern or dispersion
- May be because organisms are territorial and need space from other individuals
Random:
The position of everyone is independent of
other individuals
demographic
how the abiotic and biotic factors influence pop density and dispersion as well as
immigration, emigration, natality and mortality
- Statistics of a pop and how they change over time
Life table
summaries the survival and reproductive rates of individuals in specific age groups
Survivorship curves
- made from life tables
- useful when there is not a lot of emigration or immigration as it
shows how a population changes over time. - Reproductive rates can also be used insuch a population.
R- type survivorship curve
type 3
- low parental care -> fewer offspring survive into adulthood
- high number of offspring produced
e. g. trees, barnacle, fish
K-type survivorship curve
type 1
- > more offspring survive into adulthood
- few offspring
- high prenatal care
e. g. humans, elephants etc.
Type 2
constant death rate in the organism’s life
e.g. birds, rodents, lizards
reproductive rates
proportion of females weaning a litter x mean number of females in a litter = average number of female offspring
exponential growth model
Populations expand greatly when resources are abundant, and the resources start
reducing compared to population size
change in population size = births + immigrants entering the population - deaths - immigrants leaving the population
(LOOK AT EQUATIONS ON PRINTED NOTES)
Exponential growth:
The population increases at a constant rate per individual = J shaped
growth curve
Logistic model growth
population grows more slowly as it nears carrying capacity
LOOK AT PRINTED NOTES
A S-shaped graph is produced
The pop increases exponentially and then levels out at carrying
capacity
Assumptions of the logistic growth model:
-Populations don’t just adjust to a new environment and grow according the
model
-There is a lag effect
Life history traits are produced by natural selection
There are trade-offs between survival and reproductive traits (frequency of
reproduction, number of offspring, investment in parental care)
life history
Traits that affect an organism’s schedule of reproduction and survival make up its
Diversity of life histories:
Organisms also differ in:
- How many offspring they produce (one or many)
- How often they reproduce
Semelparity:
- Reproduce once off with lots of offspring and then
dies - Organisms that live in environments that are
unpredictable
iteroparity
- Repeated reproduction
- Environment is predictable, and they can depend on it
Trade-offs and life histories:
Organisms need to choose between conserving their energy to grow
themselves or to produce offspring
There is a trade-off between offspring number and the amount of resources
a parent can devote to each offspring
Number of offspring:
Large number of offspring with no parental care = many individuals
survive even if some are lost
Size:
- Smaller organisms are formed = less energy to give each offspring
therefore many small are formed - Smaller organisms are formed so that they can be cared for by
parents and they can grow - Organisms with high levels of being predated produces large amounts of
offspring to increase the survival likelihood - Increased parental care increases the change of offspring survival
Logistic model and life history:
Look at printed notes
- K - selected species
Density dependent
Produce and live in areas with limited resources
Organisms can extract resources better when the resources are low
There population size doesn’t fluctuate as much
E.g.: humans, mammals with parental care - R- selected species
Density independent
Live and produce in areas with maximum resources
These organisms produce lots of offspring
Resources aren’t limited
Organisms overshoot carrying capacity and fluctuate there
E.g.: trees, barnacles, fish
Population change and population density:
Population grows when birth rate > death rate
Density independent regulation:
A birth rate or death rate that doesn’t change with population
density
E.g.: climate, temperature, salinity, precipitation
Density dependent regulation:
Birth rate that decreases with a rising density or a death rate that
increases with an increase in population density
E.g.: predation, disease, competition for resources, waste,
competition for waste, space (territoriality)
Positive feedback
- between population density and the rates of births and
death - Helps stabilise a population
Negative feedback
between density dependent factors and population
density
Population dynamics:
Fluctuation of size of a population from place to place or time to time
Predator prey relationship:
Predator population never reaches the highs of the prey and they lag
behind the prey’s fluctuations
Immigration, emigration and metapopulations:
When a pop becomes crowded and resource competition increases
Emigration increases
Metapopulations:
occupy patches of suitable habitats in a place with lots of unsuitable habitats Patches vary in size, quality and isolation from other patches If all individuals from a patch die, then they will be occupied by immigrants from other patches
Global human population:
- The human population is growing faster than exponential growth
- During the agricultural revolution = movement of humans to different
countries of the world
Created food sources for people to live, survive and reproduce - Plagues decreased the population
- Industrial revolution caused population to increase as there was a rapid
increase in the amount of food produced
Regional patterns of population change:
Zero pop growth = birth rate – death rate -> stable pop’s growth
Demographic transition:
- Transition from high birth and death rate to low birth and death rate
zero pop growth = high birth rate - high death rate
↓
zero pop growth = low birth rate - low death rate
- This is caused by improved living conditions and industrialisation,
increase in the quality of health care, improved access to education
especially for women - Populations are declining because reproductive rates are below the
replacement level:
- Change this by increasing the birth rate or immigration - Education, delating marriage, contraception = moves more populations
towards zero pop growth
Age structure:
The relative number of individuals of each age in a population
Rapidly growing population:
- The base is very large, and they will grow up to reproduce and cause
more growth in the population - Triangle shaped
- Shows:
Employment and education problems will continue into the
future
Slow growing population:
- Even growth from the base till post-reproductive stages
- Rectangular shaped
- Shows:
The younger generation will be supporting the older
generation “boomers” in future
No growth population:
- Small base
- Individuals younger than the reproductive age are under represented
- The population will decrease in the future
- Bell shaped
Shows:
The younger generation will be supporting the older
generation “boomers” in future
Infant mortality
- the number of infant deaths per 1000 live births
- The higher the lower the quality of life faced by children at birth
- Parents want to make more children to ensure some reach
adulthood
Life expectancy at birth:
the predicted average length of life at birth
the lower the life expectancy the more they are affected by disease,
poor infrastructure, social upheaval
limits in human population size:
Increase in population increases the demands of resources (land, food, work,
disease spread, fuel, building materials etc)
Ecological footprint:
Land, water and resources required by each person, city or nation to
produce all the resources it consumes and to absorb all the waste it
generates
Use energy use to determine this as well
Estimates how close we are to the earth’s carrying capacity
Competition -/-:
Individuals of different species compete for resources that limits the survival
and reproduction of each species
Competitive exclusion:
One species grows to their carrying capacity and the other dies off
(inferior competitor)
Ecological niche:
the specific set of biotic and abiotic resources that an
organism uses in its environment
Sympatric populations
= geographically overlapping
Have to change their structure to use resources so as
not out outcompete or be outcompeted
Allopatric populations
= geographically separate
Use similar resources and are geographically similar
Predation +/-:
One species is the predator and the other the prey
The predators have developed adaptations to help them catch prey and the
prey have developed adaptations to escape from the predators
They both evolve in the process = evolutionary arm race =
coevolution:
coevolution:
The most efficient predators are able to get the predators
and thus survive and reproduce
The prey which escape the clutches of the predators are able
to survive and reproduce
Herbivory +/-:
- A herbivore eats the plant by harming it
- Plants may develop thorns, toxins etc.
- Herbivore develops a way of finding out which is the most nutritious food to
be eaten
Parasitism +/-:
The parasite derive nourishment from another organism (host) and harms it
in the process
Endoparasites:
Parasites that live in the host
Ectoparasites:
Parasites that live outside of the host
Mutualism +/+:
- Benefits both species
- Each species depends on the other for survival, but some can survive on
their own - Both species provide things to the other
Commensalism +/0:
One species is helped by the other which is not benefitted nor harmed
trophic structure
- Feeding relationships between organisms
- Plants and autotrophs are primary producers that transfer food energy
upwards to the herbivores (primary consumers) -> carnivores (secondary,
tertiary and quaternary consumers) -> decomposers - This forms a food chain where each position an organism occupies is called a
trophic level
Food webs:
Interconnected food chains
Species with large impact:
Species that are abundant or play a pivotal role in community dynamics
Dominant species:
Species with a lot of individuals
Key stone species:
Have an important ecological role
They may not be very dominant
Ecosystem engineers:
- Transform the landscape and ecosystem so it is suitable for the
populations in it - They do this by felling trees, making ponds, digging etc.
Bottom-up control:
- Unidirectional influence from lower to
higher trophic levels - Bottom levels control top levels
Top-down control:
- Predation controls community organisation
- Predators limit herbivores and herbivores limit plants
Biomanipulation:
Helps prevent algal blooms by altering the density of
higher level consumers
Eg: removing the fish allows the zooplankton to
increase in numbers and this decreases the algal
density
Biological control:
Controlling of pests (insects, mites, weeds etc.) using
other organisms that will resort to predatory, herbivory,
parasitism or other mechanisms to decrease its
proliferation and negative effects
Epidemiology:
Understanding disease, the patterns of disease and developing intervention
strategies
Disease ecology:
Understanding the distributions, emergence, distribution of diseases and
environmental and ecological determinants of disease
zoonotic disease
- Diseases that are transferred to humans from other animals through direct contact
with the infected animal or an intermediate species (vector)
- Vectors are mostly parasites - Identifying the community of hosts and vectors helps prevent illness
- Helps control the host that spreads the disease and prevents the
vector coming into contact with the host
reservoir habitat
Animals that carry the disease - Pathogens come into contact with the reservoir - Pathogens immigrate from the reservoir to the vertebrate body where they cause a disease
Diseases emerge because of:
- human population growth
- having exotic pets
- poor awareness of disease
- land use changes
- climate change
- bushmeat trade
Stages of pathogen evolution:
a. Viruses are transmitted by the reservoir only
b. Starts getting transmits through humans
c. Pathogen evolves into a different form and can be transmitted
to humans by humans
- Easy for humans to get diseases from primates = we share a lot of
our genome
- Body becomes the ecosystem = in which the pathogen can survive
Introducing antibiotics and vaccines = natural selection
pressure
Globalisation:
Past = humans couldn't travel, and epidemics were confined to small areas Today = people can travel easily and transmit diseases from place to place
SARS:
Caused by coronavirus and produces flu-like symptoms
Chinese rufous horseshoe bat transfers the virus to masked palm
civet and then to humans
Causes: bush meat, globalisation
The importance of niche:
Find the environmental factors that the reservoirs need to live with the
pathogen
- Helps predict the disease outbreak in other areas
Chagas disease:
- Caused by protist carried by an (carried by rodents) insect that poos on
skin and causes an itching which when scratched enters the body - Rodents carry the bugs live close to each other and the protist can be
easily transmitted
Malaria in Sahel region:
- Rain arrives and the population of the mosquito increases
- Migration of mosquitos to areas with water sources from the rain
- The mosquitos live far from the dry region and travel there
- Aestivation - hibernating
- Mosquitos sleep during the high temperatures and dry times
Control:
- Chemical and biological control
- Larvicides/adulticides
- Mosquitofish
Eat the larvae of the mosquito
Avian influenza (H5N1 virus) and bird migration:
Water birds migrate a lot globally and carry this virus from place to place
Water pollution:
Critical load in water increases due to human waste -> eutrophication
-> harmful algal bloom
Too many nutrients in the water due to human waste (from fertilizer
etc.). algal blooms occur due to the increase in nutrients and
sunlight. The water body becomes covered in algae
Prevents sunlight entering the lower levels of water and algae
use up all the oxygen
Biological magnification:
Organisms in the lower trophic levels consume or are exposed to chemicals
and toxins
The toxins may be consumed in small quantities and may not affect
the organism that consumes it
Organisms in higher trophic levels consume those animals and are affected
by those toxins
Have a higher concentration of the toxins
The concentration builds up going up the trophic levels
Biological magnification = building up of toxins in organisms in trophic levels
E.g.: DDT
Goes into the water -> consumed by zoo plankton -> small fish eat
the zoo plankton and consume a higher concentration of DDT ->
larger fish eat the smaller fish -> birds eat the fish with the higher
concentration of DDT and have a lot of the DDT in their diet due to
the accumulated DDT concentration
Acid rain:
Rain has high levels of nitric and sulphuric acid
Burning fossil fuels -> sulphur dioxide and nitrogen oxides are released into
the atmosphere -> react with water and oxygen and form nitric and
sulphuric acid -> during precipitation it falls with the rain water
Effects:
- Makes water bodies more acidic
- Aluminium is absorbed from the soil
- Toxic conditions are created, and aquatic animals are affected
Climate change:
Gases that cause the greenhouse effect 1. Water vapour 2. Carbon dioxide 3. Methane 4. Nitrous oxide 5. Oxone 6. Chlorofluorocarbons 7. Hydrofluorocarbons - The gases cause more heat to be trapped in the earth’s atmosphere and causes a change in climate, increase in water levels due to ice caps melting - Due to climate change more diseases emerge from the icecaps = zombie viruses are released
- Diversity decreases because organisms cannot survive properly in the fast-
changing environments
