Population size and ecosystems (C1)

Question 1

Ecology definition

Answer 1

the study of living organisms within a habitat and their interactions with both biotic and abiotic factors

Question 2

Ecosystem definition

Answer 2

a characteristic community of interdependent species interacting with the abiotic components of their habitat

Question 3

Habitat definition

Answer 3

the place in which an organism lives

• often contains a community of organisms

Question 4

Population definition

Answer 4

a group of interbreeding organisms of the same species occupying a particular habitat

Question 5

Community definition

Answer 5

interacting populations of two or more species within a particular habitat

i.e populations of different species living within the same habitat

Question 6

Biotic factors

Answer 6

living factors within the environment including…

• competition for recourses
• predators
• disease/ pathogens

Question 7

Abiotic factors

Answer 7

non living factors including…

• light intensity
• water/nutrients/o2 availability
• temperature

Question 8

Niche definition

Answer 8

the specific role and position a species plays within a particular ecosystem

Question 9

Random sampling

Answer 9

method of sampling when abiotic factors are uniform

Question 10

Systematic sampling

Answer 10

method of sampling when there is a change is abiotic factors

Question 11

What are population numbers dependent on?

Answer 11

population numbers will fluctuate, this is dependent on various factors, including…

• birth rates/cell division
• death rates
• immigration
• emigration

Question 12

Name the shape of the graph of a usual pattern of growth of an equilibrium species

Answer 12

S-shaped

sigmoidal

Question 13

What are the phases of the population growth curve for an equilibrium species and what happens?
*draw the graph

Answer 13

1. LAG - slow rate of reproduction, cellular activity but not growth, a period of intense metabolic activity like enzyme synthesis i.e reaching sexual maturity in animals, time taken for yeast to hydrate in nutrient broth
2. LOG/EXPONENTIAL - rapid increase in population, no factors limiting growth
3. STATIONARY - birth rate/cell division is equal to death rate, factors are limiting further growth, pop has reached carrying capacity
4. DEATH/DECLINE - environmental factors result in death rate greater than birth rate/cell division i.e glucose depleted in nutrient broth or yeast producing toxic waste ethanol

Question 14

Carrying capacity definition

Answer 14

the maximum number of individuals a population can sustain within a particular environment
(the actual number fluctuates around the carrying capacity in response to environmental changes)

Question 15

Where is environment resistance and where does it start to occur?

Answer 15

• any factors that may limit the growth of a population

- end of log phase

Question 16

How do you calculate population changes when populations are plotted on a log scale?

Answer 16

number of bacteria at one specified day
number of bacteria at the other day
antilog10 those numbers
take away from each other
divide over the difference of days

i.e antilog10 ? - antilog10 ??
————————————–
day/time difference

Question 17

What are density dependent factors affecting the size of a population?

Answer 17

• the larger the population size the greater the effect (more likely to slow down pop growth rate)
  e.g…..
  • disease and parasites
  • food availability
  • toxic waste build up
  (often biotic)

Question 18

What are density independent factors affecting the size of a population?

Answer 18

• factors have an effect regardless of population size, the effect is ‘independent’ to the population
  (more likely to cause a population crash)
  e.g…..
  • natural disaster i.e volcanic eruption, eq, floods etc..
  • sudden changes in temp
  • hunting
  (often abiotic)

Question 19

How can competition affect population size, and the types of competition?

Answer 19

• by impacting potential breeding success (comp for mates) and survival of organism (comp for land, food, fight)

1. INTRA - specific competition
2. INTER - specific competition

Question 20

Factors affecting population size (3)

Answer 20

• density dependent factors
• desntisy independent factors
• competition

Question 21

What is INTRA specific competition?

Answer 21

(comp between the same species)

• between members of the SAME species, occupy same niche/specific habitat, compete for same recourses
• driving force behind natural selection ( as n.s is survival of fittest between that single species - pass on beneficial alleles, variation, adaption can occur)
• as pop of that species a greater proportion of individuals fail to survive because comp excels

Question 22

What is INTER specific competition?

Answer 22

(comp between different species)

• competition for resources between members of different species
• in general one species will out compete the other

Question 23

What is the definition of niche and its concept?

Answer 23

NICHE - the specific role and position a species plays within a particular ecosystem

• only one species can occupy a particular niche within an ecosystem - one species will always outcompete the other
e.g two different species of protozoan grown in lab flasks - grow well in flasks separately but when grown together one outcompetes the other for nutrients, the population of one grows and the other falls

Question 24

What is the concept of an ecosystem?

Answer 24

ECOSYSTEM is a characteristic community of interdependent species and their habitat

*ecosystems range in size from very large to very
small

Question 25

What is the source of energy for an ecosystem?

Answer 25

* the SUN is the source of energy for an ecosystem * light energy, trapped by photosynthesis is the source of energy for most ecosystems (other than those based on chemosynthesis, e.g. hydrothermal vents)

Question 26

What are trophic levels? energy between? biomass?

Answer 26

feeding levels within an ecosystem, the level at which an organism falls within the food web - producers are the first trophic level i.e photosynthesising plants - then a series of consumers (4/5 levels - only enough energy to support) - flow is energy is shown between the levels from the initial energy source, the sun to producers and consumers - energy is lost between trophic levels - biomass decreases up the levels

Question 27

What is gross primary productivity (GPP)?

Answer 27

Gross primary productivity (GPP) is the rate of production of chemical energy in organic chemicals by photosynthesis (in kJ m-2 year-1).

Question 28

What is net primary productive (NPP) and its equation?

Answer 28

Net Primary Production is gross primary production minus the chemical energy generated in respiration and used up by the producers metabolism in the year (respiration = R) (NPP = GPP - R) *NPP represents the potential food/chemical energy available to heterotrophs in ecosystems.

Question 29

Why is energy lost from the food chain at each level?

Answer 29

* energy is egested - mostly cellulose as indigestible * energy lost as heat during respiration (farmers keep animals inside during winter - less energy lost regulating body temp) * energy remains in inedible parts of the animal - fur, bones, horns *INEFFICIENCY OF ENERGY TRANSFER BETWEEN TROPHIC LEVELS

Question 30

Primary productivity vs secondary productivity

Answer 30

- primary productivity involves the producers - secondary productivity involves the rate at which consumers accumulate energy from assimilated food in biomass in their cells/tissues

Question 31

Why do carnivores have a more efficient energy conversion than herbivores?

Answer 31

protein is more rapidly and easily digested than cellulose which is lost in much of herbivores faeces

Question 32

What is gross ecological efficiency? equation?

Answer 32

measure of how much energy is transferred from one trophic level to the next (often around 10% but oceanic food chains higher approx. 40%) GEE = energy in that trophic level -------------------------------------------- x 100 energy in previous trophic level