Populations in ecosystems Flashcards
1
Q
Define ecology
A
- the study of interrelationships between organisms and their environment
2
Q
Define abiotic
A
- non living components of the environment
3
Q
Define biotic
A
- living components of the environment
4
Q
Define species
A
- a group of organisms that are similar in terms of shape, physiology, genetics and behaviour which can interbreed to produce fertile offspring
5
Q
Define ecosystem
A
- dynamic systems/units mad up of a immunity and all the interacting biotic and abiotic features in that specific area. Energy flows and there is cycling of elements within the system. These systems can rage from very small to fairly large
6
Q
Define population
A
- group of interbreeding organisms of one species that occupy the same habitat at the same time
7
Q
Define community
A
- populations of different species living and interacting in a particular place at the same time
8
Q
Define habitat
A
- place where an organism normally lives, characterised by physical conditions and the other types of organisms present
9
Q
Define microhabitat
A
- smaller units within a habitat with their own microclimate
10
Q
Define niche
A
- term used to describe how an organism fits into its environment (where it lives and what it does there) this includes all the abiotic and biotic conditions to which the organism is adapted an how the organism responds/behaves to them
11
Q
Define natural ecosystem
A
- an ecosystem not managed or altered by human activity
12
Q
Define artificial ecosystem
A
- an ecosystem that is managed or altered by human activity
13
Q
Define intraspecific competition
A
- individuals of the same species compete with one another for resources (eg. Water, food, breeding sites). Availability of these resources determines population size
14
Q
Define interspecific competition
A
- Individuals of different species compete for resources (eg. Food, light, water)
15
Q
Which factors are biotic?
A
- food availability
- predators
- competition from other organisms
- infection from pathogens
16
Q
Which factors are abiotic?
A
- sunlight
- temperature
- pH
- water
- minerals
- salinity (salt levels)
17
Q
Bird species occupying different niches in the same habitat - The question is, how?
A
- These different species occupy different niches in the same ecosystem to reduce interspecific competition. They feed on different species (biotic condition) and at different water depths (abiotic condition) .
18
Q
Way affects the size of a population?
A
- Limiting factor
- Carrying capacity
19
Q
What is a limiting factor?
A
- when the rate of a natural process is affected by a number of factors, the limiting factor is the
one whose magnitude limits the rate of the whole process – often it is the factor in shortest supply.
20
Q
What is carrying capacity?
A
- the maximum population size that can be maintained over a period of time in a particular
habitat
21
Q
What can be classed as a limiting factor for a population?
A
- pH
- Water
- light
- carbon dioxide
- predators
- disease
- space
- mates
- food
- oxygen
22
Q
What affects the size of a population?
A
- food supply
- predation
- disease
- climate change
23
Q
How does food supply affect the size of a population?
A
- Large amount of food = organisms can breed more successfully.
- Food shortage = higher death rate which results in a slow or negative population growth.
24
Q
How does predation affect the size of a population?
A
- Organisms which have lots of predators will have a slower rate of population growth as more will be killed by predators
25
Q
How does disease affect the size of a population?
A
- Reduces the population by killing organisms. In densely populated areas, disease can spread quickly = may wipe out large population
26
Q
How does climate change affect the size of a population?
A
- Organisms that cannot adapt to changes in climate are less likely to survive, reproduce and pass on advantageous alleles
27
Q
Draw and label the standard growth curve
A
- organisms acclimatising to new conditions- very few individuals
- Reproduction rate is low as is the growth of the
population - lag phase
- Rapid increase in population– growing conditions are favourable with plentiful resources. Rate of reproduction is greater than
mortality rate - Log/exponential phase
- stationary phase
- rate of growth equal to rate of death
- Stable population; minor fluctuations from changing environment
- Carrying capacity of the environment
- decline/death phase
- Death rate is greater than rate of generation
28
Q
What are the abiotic factors affecting the size of a population?
A
- light
- temperature
- pH
- water and humidity
29
Q
How does light affect the size of a population?
A
- More light = greater rate of photosynthesis: greater rate of plant growth + seed production. Carrying capacity for plants increased (+ animals that feed on them)
30
Q
How does water and humidity affect the size of a population?
A
- Humidity affects transpiration rate, and so limited populations found where water is scarce. Only species able to adapt to dry conditions thrive
31
Q
How does pH affect the size of a population?
A
- Populations of organisms thrive where pH is close to their optimum. As pH affects enzyme action, only certain species adapt to regions with particular pH values
32
Q
How does temperature affect the size of a population?
A
- Carrying capacity reduced in plants + cold blooded animals if temperature not close to optimum: enzymes work slowly & metabolic activity reduced – high temps could lead to denaturation.
- Carrying capacity also reduced in warm blooded animals if conditions far from optimum: more energy expended in maintaining body temp – therefore less energy used for growth and reproduction
33
Q
What is Gause’s competitive exclusion principle?
A
- Where populations of two species occupy the
same niche, one will normally have an advantage over the other. If conditions remain the same this will lead to interspecific competition and the
removal of one species
34
Q
Why is it difficult to prove that competition could be the reason for variations in population?
A
- There are many other factors that influence population size e.g. abiotic factors.
- A causal link has to be established to show that
competition is the cause of an observed correlation. - There is a time lag in many cases of competition.
- Data on population sizes are not always reliable
35
Q
Give examples of characteristics of predators
A
- Camouflage (hide in surroundings)
- Biological ‘traps’ nets, webs
- Enhanced sound detection + a little patience
- Echolocation
- Speed (short bursts) , & sheer power
- High intelligence
- Enhanced sense of smell
- Poisons such as venom
- Ability to sense body heat
- Sharp teeth & claws
36
Q
Give examples of characteristics of prey
A
- Camouflage (hide in surroundings)
- Disguise & distraction
- Protective ‘armor’ for defense
- Poisons + aposematic colour
- The ‘playing dead’ tactic
- Strength in numbers
- Incredible speed to escape
- Mimicry (may be toxic or non-toxic)
37
Q
Why is there a lag of 1-2 years between the lynx
and the hare?
A
- Predator numbers take time to establish after an increase in prey
38
Q
Predator-prey relationships are dynamic. Describe & explain what this means
A
- Dynamic: ever-fluctuating, with predator/prey
influencing one another’s evolution
39
Q
What are the three basic principles of population of predator and prey?
A
- Predation occurs when one organism is consumed by another.
- Predators have evolved and adapted to catching their prey.
- Prey have evolved to avoid predators
40
Q
explain the shape of the curve at points 1- 5
A
- Point 1 – increase in prey numbers, few predators and limited intraspecific competition for resource
- Point 2 – increase in predator numbers as more food available; steady increase in reproduction rate
- Point 3 – decline in prey numbers due to hunting from predators, but also competition for the resources available (birth rate < death rate)
- Point 4 – decrease in predator numbers as
prey population has fallen; competition for food, space etc ; some predators will have to migrate from habitat to find food - Point 5 – subsequent increase in prey numbers as there are now fewer predators and with smaller prey numbers, there is less competition for resources
