Ecology Part 3

Question 1

Population

Answer 1

A group of organisms of the same species inhabiting the same area at the
same time

Question 2

Community

Answer 2

Interacting populations occupying the same area

Question 3

Ecological species

Answer 3

A set of organisms occupying the same niche

Question 4

Biological species

Answer 4

Closely related organisms capable of interbreeding and producing fertile
(viable) offspring

Question 5

How is Population size (number of individuals in a population) affected?

Answer 5

Birth (increases population size)

Death (decreases population size)

Migration (increases or decreases population size)

Question 6

What is recruitment?

Answer 6

Number of birthed offspring attaining maturity (added adults)

Question 7

What is Biotic Potential?

Answer 7

Maximum rate at which population can increase in ideal conditions

Question 8

What is Environmental Resistance?

Answer 8

Set by a combination of biotic and abiotic factors

Establishes the Carrying Capacity (max population size supported)

Question 9

What is biotic potential detailed?

Answer 9

Rate at which population increases in ideal conditions

No competition
Unlimited resources
Therefore, unrestricted exponential growth

Question 10

Which are the influential factors of biotic potential?

Answer 10

Age at sexual maturity

Average frequency of reproduction

Average number of offspring produced per batch

Average reproductive life span

Average death rate under ideal conditions

Question 11

What happens in Exponential Growth? (Biotic Potential)

Answer 11

Growth without limits

Question 12

What happens in Logistic Growth? (Environmental resistance)

Answer 12

Competition limits growth.

Question 13

What is environmental resistance and some examples?

Answer 13

Environmental limits set by biotic and abiotic factors

Food availability
Habitat space
Competition (intraspecific and interspecific)
Disease
Parasitism

Increases death rate and lowers birth rate
Balances population size around an ideal density
Population quickly reaches set limit and then fluctuates around it

Question 14

What are growth curves?

Answer 14

Graphical representation of population growth

Population growth pattern is often repetitive on a small scale

Many mini booms and mini busts (depending on environmental resistance)
Graphs more complex than simple curve

Question 15

Factors of an S Shaped (Sigmoid) Growth Curve?

Answer 15

Density dependent growth

As numbers increase, growth slows down

Question 16

Factors of a J Shaped Growth Curve?

Answer 16

Density independent growth

Growth continues to speed up exponentially until the carrying capacity is exceeded

Question 17

J-Shaped Growth Curve (detailed)

Answer 17

Lag phase is followed by a log phase until the population suddenly crashes

Also called the “boom and bust” cycle

Growth is Density Independent
Population grows quickly and then crashes
this cycle is repeated incessantly

Influential factors include:
Seasonality, breeding phases, human intervention (e.g. pesticides), seasonal climatic extremes (e.g.floods, fires or droughts)

Question 18

what is the exponential growth equation?

Answer 18

dN/dt = rN

Question 19

S-Shaped growth curve (detailed)

Answer 19

Growth is Density Dependent

Curve is Logistic

Lag phase (slow growth due to adjustment and few numbers)
Log phase (max birth rate growth speeds up as numbers increase)
Deceleration phase (environmental resistance increases with increasing density)
Stationery phase (recruitment and death even out)

Saturation Value or Carrying Capacity is reached

Death phase (death rate exceeds birth rate due to increasing environmental
resistance)

Fast growth when density is low; slow growth when density is high
Influential factors include competition, (including predation) parasitism (including disease), overcrowding and stress

Question 20

What is the logistic growth equation?

Answer 20

dN/dt = rN (K-N/K)

Question 21

Which are the population strategies?

Answer 21

r-strategist

K-strategist

Question 22

What are opportunist species?

Answer 22

Also called r selected species or r strategists

high growth rate

produce many offspring with low probability of surviving

Exploit less crowded ecological niches

Predominate in disturbed or unstable environments

Question 23

What are Equilibrium species?

Answer 23

Also called K selected species or K strategists

Low growth rate

Produce few offspring with increased probability of survival

Better competitors (can survive in more crowded niches)

Predominate in stable and predictable environments

Question 24

How many Survivorship Curves types are there?

Answer 24

3 types of curves

Question 25

Explain type 1 curve

Answer 25

High probability of survival throughout their life with a sudden drop at a specific age Parental care, low birth rates, and extended social networks (herds, packs, or colonies) improve survival rates E.g. Elk, White tailed Deer, Grey Wolves, and Humans

Question 26

Explain type 2 curve

Answer 26

Steadily declining probability of survival throughout their life Parental care, moderate to low birth rates, and extended social networks but small to moderate in size and are a key prey source of prey E.g. Sandhill Cranes and Coyotes

Question 27

Explain type 3 curve

Answer 27

Very rapid decline in probability of survival early in life and then a good probability of survival late in life Large body size or physical/behaviour defence mechanisms E.g. Northern Pike, Water Hyacinth, and Autumn Olive

Question 28

Population size information card

Answer 28

Population size fluctuates even when stable Abiotic and biotic factors continue to influence population size Sometimes these factors are cyclical Some factors affect birth rate (population growth) Other factors affect death rate (population decline)

Question 29

Intraspecific factor- Density Dependent Factors (mostly biotic)

Answer 29

Effect increases with increasing population density E.g. food shortage, territorial behaviour, overcrowding and dispersal

Question 30

Intraspesific factor- Density Independent Factors (mostly abiotic)

Answer 30

Effect is not related to population size E.g. edaphic factors, climatic factors, natural disasters, and pollution

Question 31

Food Shortage information card

Answer 31

Individuals suffer the effects of malnutrition Increased mortality Especially young Reduced resistance to disease and parasites Reduced fecundity (or altogether absent) Inherent defensive behaviour may be lost In severe starvation cases, animals may seek food beyond adequate cover against discovery by predators This leads to increased mortality through predation Water shortage is just as debilitating

Question 32

Territorial Behaviour (Territoriality) information card

Answer 32

Low population density One or both individuals in a pair establish a territory The extent of the territory is marked chemically, visually, or through calls Challengers are seen off after a ritual fight There is no overlap between individual territories High population density Territorial size diminishes Only the toughest maintain adequate territories These individuals survive and/or reproduce to the detriment of others of the same species (Intraspecific Competition) This is also called Regulation through Spatial Interaction

Question 33

Overcrowding information card

Answer 33

Low population density Population behaves normally High population density Effects of Social Stress are observed in small mammals Diminished reproductive organs Reduced reproductive rate Slower growth Reduced disease resistance Reduced parental care Young abandon nest early and die more often as a consequence Cannibalism of the young (Intraspecific Competition) These symptoms appear even in cases of high food availability

Question 34

what are examples of interspecific interactive relationships?

Answer 34

Predator prey relationships Parasite host relationships Interspecific competition for resources

Question 35

Predator-Prey interactions

Answer 35

Predator species feed on their designated prey species Predators control prey populations This is a density dependent interaction

Question 36

Experiments in the lab show that predator and prey populations interactions follow a distinct pattern

Answer 36

1. A crash in a prey population leads to a similar predator population crash 2. The reduced number of predators boosts the prey population which recovers 3. The now abundant prey population boots the predator population 4. The increase in predators cause the prey population to crash (cycle complete) The two populations are slightly out of sync it takes some time for the effect to be felt Lab conditions preclude predators selecting alternative prey so field results could be different (also, other density dependant factors may apply, e.g. disease and overgrazing)

Question 37

Parasite-Host Interactions information card

Answer 37

Parasites only attack designated host species Parasites weaken hosts and may make them more vulnerable to disease or predators This is another density dependant interaction Overcrowding means parasites spread faster and wider Under normal circumstances, parasites have limited mobility Many parasitic strategies have evolved E.g. conventional parasite, parasitoid and parasitic castrator

Question 38

Interspecific Competition

Answer 38

Predators and parasites keep populations within the k limit They cull the least fit individuals Only most fit individuals survive to reproduce Target species involved in “arms race” with predators and parasites This is called Coevolution It is a major evolutionary drive

Question 39

Keystone Species

Answer 39

• Disproportionately large effect on the community Maintain biodiversity by controlling dominant species Provide critical resources for a wide variety of species Fundamental community structure changes if this species is removed Not all communities include keystone species If present, they are critical to the environment and community

Question 40

Examples of keystone species

Answer 40

E.g. Pisaster ochraceus (starfish) Major predator of the mussel Mytilus When the starfish is removed, mussels take over the community and displace the other 25 or so species of invertebrates and algae in the environment Other examples Sea otters and sea urchins; grey wolves in the Greater Yellowstone ecosystem

Question 41

Ecological Niche

Answer 41

How an organism utilises its environment E.g. spatial utilisation, food consumption, temperature range, mating requirements, moisture conditions, etc

Question 42

Fundamental (Potential) niche

Answer 42

Full range of conditions in which organism can survive

Question 43

Realised (Actual) niche

Answer 43

Actual range of conditions occupied by the organism

Question 44

Chthalamus vs Semibalanus information card

Answer 44

Study carried out along the coast of Scotland Competitive interactions between two types of barnacles Chthalamus stellatus can withstand a wide range of submersion/exposure However it is the weaker competitor Semibalanus balanoides cannot withstand long exposure It is the stronger competitor If present alone, C . stellatus occupies the shallow and deep zones The presence of S . balanoides in deeper zones prevents C . stellatus from occupying its full niche as it is outcompeted

Question 45

Niche Strategies- Generalist Species

Answer 45

Characteristics Wide fundamental niche Can exist in many different environments Can use a wide range of resources Good opportunistic species Generally successful at colonising new environments Good at surviving environmental changes Can tolerate a wide variety of conditions Generally evolve at a faster pace Tend to be put under greater environmental pressures Examples Omnivores, humans, weeds

Question 46

Niche Strategies-Specialist Species

Answer 46

Characteristics Narrow fundamental niche Can exist only in specific environments Limited to a narrow range of resources Often equilibrium species Need stable environment Generally outcompete the generalists Not likely to survive environmental changes Narrow tolerance limits More vulnerable to extinction Not likely to be flexible enough to survive change Examples Pandas, koalas, giraffes, xerophytes