L1 Abiotic and biotic drivers of ecological patterns and processes

Question 1

Abiotic variables determine which type of niche?

Answer 1

The fundamental niche
Abiotic variables determine the performance of living organisms.

Question 2

Biotic variables determine which type of niche?

Answer 2

The realised niche
Biotic variables determine the distributions and functions of organisms in nature.

Question 3

Organisms are adapted to a set of physical and chemical conditions which act as physiological controls on their growth and survival.

For example, which condition can affect the following 4 organismal aspects?
A - Enzyme activity
B - Scope for work (Rate of respiration)
C - Individual growth rate
D - Population growth rate

Answer 3

Temperature

Question 4

Performance curve windows.

Organisms can ________ under a wider range of conditions, than they can grow in.

But they can grow under a wider range of conditions than they can ____________.

Answer 4

Organisms can __SURVIVE__ under a wider range of conditions, than they can grow in.

But they can grow under a wider range of conditions than they can __REPRODUCE__.

Question 5

Performance curve windows
What does a bell curve show?

Answer 5

It relates environment to performance of an organism

Question 6

Performance curve 1

In a typical bell curve, where would the conditions:
S - Survival
G - Growth
R - Reproduction
be found at different heights on the bell curve?

Answer 6

An individual’s survival would be the lowest (widest) band of the bell curve as this basic minimum is easily maintained.

An individual’s growth is the middle segment band as they can still grow under a wide range of environmental conditions but less than if they just needed to survive.

Reproduction is in a very narrow banded window spanning the tip of the bell curve. R is the least intense condition, meaning they can reproduce under the least amount of conditions when performance is compromised.

To summarise,
Extreme conditions are lethal.
Less extreme conditions prevent Growth.
Only optimal conditions = Reproduction.

Question 7

Performance curve 2

This figure sees a plateaued line slope downwards till the x axis like a rollercoaster. Reproduction is seen to stop first, followed by growth, and lastly survival.
What does this mean?

Answer 7

Whatever condition is affecting the individual, is lethal, but only at high intensities. The declining slope is due to the increasing environmental variable, which causes low performance as a result. e.g. pollutants and heavy metals are fine under low conc but at high levels are bad.
The reproduction-growth-survival sequence still applies.

Question 8

Performance curve 3

This figure sees a steep increasing line basically touching the y axis, it then plateaus. This plateaued line slopes downwards till the x axis like a rollercoaster. Reproduction is seen to stop first, followed by growth, and lastly survival.
What does this mean - how is it different from curve 2 that lacked the first steep increase?

Answer 8

Similar to curve 2, but the condition is required by organisms as a resource at low concentrations. It’s only when it gets too high it becomes an issue and the reproduction-growth-survival sequence applies.
e.g. copper, needed for survival but becomes toxic at high levels.

Question 9

The ecological niche. Who modelled the life of an organism in 1933?

Answer 9

Elton

Question 10

What is meant by the set of ‘conditions’ Hutchinson 1957 created to define where an organism can live?

Answer 10

This set of conditions looks at how tolerances and requirements interact to determine what conditions and resources are needed by an organism to practice its way of life.

Question 11

An organism will inhabit areas within hypervolume provided what 3 things?

Answer 11

1. Accessibility
2. No preclusion by other organisms
3. Fundamental vs realised niche

Question 11

What is an n-dimensional hypervolume?

Answer 11

When more than 2 conditions impact an organism.
In the hypervolume it’s the physical and chemical environment being considered

Question 12

Define ecological niche

Answer 12

The role an organism plays in a community

Question 13

Define fundamental niche

Answer 13

The full range of environmental conditions and resources that a species can occupy and use, without any limiting factors.

Question 14

Define realised niche

Answer 14

A subset of the fundamental niche.
Is the result of the presence of limiting factors (such as food, light, the presence of other species etc.) forcing an organism to move to certain environments where it may thrive.

It’s where the organism can live after we’ve taken into account its interaction with other organisms (preclusion effect).

Question 15

Which type of habitat are useful in understanding how abiotic factors affect species distribution?

Answer 15

Shore habitats e.g. rocky or sheltered

Question 16

On rocky shores there is a characteristic pattern of ___________.

Answer 16

Zonation

Question 17

On sheltered shores, zonation is mainly seen in _____.

Answer 17

algae

Question 18

What is an example of algae zonation in the case study of Schonbeck & Norton (1978)?

Answer 18

The regression of brown algae fucoids as we move up the shore.

Question 19

When are high shore species more adapted to desiccation?

Answer 19

During germination and in their growth

Question 20

The reproduction strategies of high shore species are more adapted to which shore height?

Answer 20

upper shore

Question 21

The figure below shows number of gametes released after different periods of exposure to air. The lower shore species required a longer period of exposure to air before releasing gametes.

Which author’s publication produced the figure relating to that finding?

Answer 21

Baker 1910

Question 22

What was a controlled observation made in relation to the die backs of Fucus spiralis in Schonbeck & Norton’s 1978 study?

Answer 22

Fucus spiralis die backs occurred a few weeks after periods of hot, dry weather coinciding with daytime spring low tides.
(meant intense exposure to air)

Question 23

What is a controlled observation used for?

Answer 23

Used to see what happens in the environment

Question 24

Schonbeck and Norton 1978, how did they manipulate Fucus spiralis?

Answer 24

They manipulated Fucus spiralis by taking it up shore.
Findings: After moving it up shore it grew slowly before it ultimately died.

Question 25

In the manipulated study what were the controls of the Schonbeck and Norton 1978 study?

Answer 25

Take a Fucus spiralis plant from the zone it originated from, once taken put it back in the zone to see what happens.

They did transplants down shore too

Question 26

Yes abiotic factors USUALLY dictate upper limits of some species in the intertidal. But why might they not?
References to the Schonbeck and Norton 1978 study.

Answer 26

1. Complex interactions between factors.
2. Not always true for all species (See Raffaelli and Hawkins book).
3. What life stages are we referencing? Are some influenced in different ways?
4. Have we found that desiccation is important? Is that why Fucus spiralis didn’t like the upper shore? Was it due to harsh exposure to environmental conditions like temperature?
5. Do we know enough about the shore environment?
6. What about microhabitats?

Question 27

But what about lower limits? Schonbeck and Norton 1978 took it further with a canopy removal experiment.
They removed all algae from the shore. All species came back but not in their normal zonation.

So…can we accept or reject the hypothesis: that abiotic factors limit the lower zones?

Answer 27

Can REJECT hypothesis. Means the evidence present wasn’t substantial enough to say that abiotic factors limit the lower zones

Question 28

Define amensalism

Answer 28

One organism is negatively affected while the other is unaffected.

Negatively affected could be a decrease in survival/fitness.

Question 29

Define commensalism

Answer 29

One organism benefits and the other is unaffected.

Question 30

Define mutualism

Answer 30

Where both organisms involved benefit from the relationship.

e.g. pollination by insects, where the plant receives reproductive assistance and the insect receives nectar or pollen as food.

Question 31

Define antagonism

Answer 31

Where one organism actively harms or inhibits another organism.

This can occur through competition for resources, predation, parasitism, or allelopathy, where one organism releases chemicals to inhibit the growth of others.

Question 32

Define competition

Answer 32

Interaction between individuals brought about by a shared requirement for a resource and leading to a reduction in the survivorship, growth and/or reproduction of at least some of the competing individuals concerned.

Question 33

What is the difference between exploitation competition and interference competition?

Answer 33

Exploitation competition involves organisms competing for resources by using them up, while interference competition involves direct interactions that prevent access to resources.

Question 34

What is the difference between intraspecific competition and interspecific competition?

Answer 34

Intraspecific competition occurs between individuals of the same species for resources, while interspecific competition occurs between individuals of different species for resources.
Intra = SAME species
Inter = BETWEEN species

Question 35

Key study: Does competition with Semibalanus balanoides exclude Chthamalus montagui from low shore?
Who was the author?

Answer 35

Connell 1961

Question 36

What were Connell (1961)’s observations?

Answer 36

When the two species of barnacle both settle, they are both found over a range of shore heights.

They both settle widely. The adult distributions much more restricted to higher shore in terms of Chthamalus.

Question 37

What was Connell 1961 hypothesis?

Answer 37

That Chthamalus montagui was restricted due to presence of Semibalanus balanoides.

Question 38

How did Connell 1961 test his hypothesis?

Answer 38

His hypothesis – was that Chthamalus was restricted due to presence of Semibalanus.
He monitored populations. Did a manipulation. He grew Chthamalus at different levels of the shore both with the Semibalanus and also after removing Semibalanus.
Looking at changes in Chthamalus populations over time in different shores.

Question 39

What were Connell 1961’s findings?

Answer 39

His hypothesis – was that Chthamalus was restricted due to presence of Semibalanus.

Method - He monitored populations. Did a manipulation. He grew Chthamalus at different levels of the shore both with the Semibalanus and also after removing Semibalanus. Looking at changes in Chthamalus populations over time in different shores.

Findings - Found it didn’t matter whether Semibalanus was present or not, Chthamalus did fine.
In terms of competition: as you move down the shore Chthamalus did fine as long as Semibalanus was removed.
If Semibalanus wasn’t removed, the Chthamalus decline.
This suggests there is some restrictive competition at the lower limits of the Chthamalus.
CLASSIC EXAMPLE OF ROCKY SHORE COMPETITION.

He found that interspecific not INTRASPECIFC competition, caused death. So when they were crowded out they died out. Only the small misshapen Chthamalus survived.

Question 40

So what was the main finding of Connell 1961?

Answer 40

He found that INTERSPECIFIC comp (between species) caused death. So when they were crowded out they died out. Only the small mis-shapen Chthamalus survived.

The Semibalanus grew quicker on lower shore.

Question 41

Does competition with Semibalanus balanoides exclude Chthamalus montagui from low shore?

Answer 41

• Interspecific (not intraspecific) competition important cause of death in Chthamalus.
• Chthamalus surviving in plots with Semibalanus were often small & mis-shapen.
• Growth of Semibalanus faster than Chthamalus on low shore levels.
• Growth of Semibalanus decreased at higher shore levels.
• Found strong evidence for distributions in nature

Question 42

In terms of niche theory, considered the competitive exclusion principle (Gause).
— What is the competitive exclusion principle?

Answer 42

“If two competing species coexist in a stable environment, they do so as a result of niche differentiation (differences in realised niche).
If there is no such differentiation, or if it is precluded by the habitat, then one competing species will eliminate or exclude the other.”

BASICALLY - is saying that 2 species can’t occupy the same niche at the same time, they must split it up or one goes away, or they both adapt to each other and change their niches.

Question 43

Limitations of the competitive exclusion principle (Gause)?

(definition reminder: 2 species can’t occupy the same niche at the same time, they must split it up or one goes away, or they both adapt to each other and change their niches.)

Answer 43

• Sometimes hard to test
• Niche differentiation may not always arise from interspecific competition (between species).
• Interspecific competition does not always lead to a differentiation of niches
• Non-equilibrium systems: a role for environmental heterogeneity.

Unless the system reaches equilibrium, there is likely to be competitive exclusion.

Question 44

Competitive exclusion vs coexistence

Outcomes of Lokta-Volterra models with two species show that COEXISTENCE IS POSSIBLE under certain conditions.
What are some of these?

Answer 44

–> Dominance-controlled community
–> Founder-controlled community
–> Species coexist (both are weak interspecific (between sps) and strong intraspecific (within sps) competitors)

Question 45

In terms of Lokta-Volterra model outcomes and 2 species coexisting: Define what is meant by a DOMINANCE-controlled community.

Answer 45

One species is a stronger interspecific competitor than the other: The other species is driven to extinction

 A strong competitor and a weaker one: the weaker one is driven to extinction.

Question 46

In terms of Lokta-Volterra model outcomes and 2 species coexisting: Define what is meant by a FOUNDER-controlled community.

Answer 46

Both species are STRONG interspecific and weak intraspecific competitors. One species dominates, depends on initial density.

 If both is strong with little competition in between the species, one will dominate but it depends on who gets there first. Known as founder-controlled communities

Question 47

In terms of Lokta-Volterra model outcomes and 2 species coexisting: Define what is meant by COEXISTING species

Answer 47

Both species are WEAK interspecific and strong intraspecific competitors.

 Third example is coexistence, when both are bad at competing with each other but lots of competition within (intra), this overwhelms and means both can coexist.

Question 48

What is an example of founder-controlled communities?

Answer 48

Reefs and Damselfish
e.g. coral heads, each one is colonised by a different community.

Question 49

Predation: The prey must be alive otherwise its known as _____________

Answer 49

Scavengers

Question 50

Define Predation (Begon et al. 2006)

Answer 50

“Consumption of one organism (the prey) by another organism (the predator), in which the prey is alive when the predator first attacks it.”

Question 51

3 examples of Grazers

Answer 51

Limpets
Urchins
Flatfish

Question 52

3 examples of True predators

Answer 52

Mako shark
Lionfish
Flatfish
Parasites often act as predators too

Question 53

How might predation control organism distribution? (Case study 3 - starfish pop affected the fauna distribution of barnacles and limpets further down shore. mussels were mid shore)

Predation: Pisaster limits down shore extension of Mytilus.
Who was the author?

Answer 53

Paine (1974)

Question 54

Case study 3 - (starfish pop affected the fauna distribution of barnacles and limpets further down shore. mussels were mid shore).

Predation: Pisaster limits down shore extension of Mytilus. Paine 1974.
What was his hypothesis?

Answer 54

Hypothesis – the predation of the star fish prevents mussels down the shore.

Question 55

Predation: Pisaster limits down shore extension of Mytilus. Paine (1974)
Hypothesis – the predation of the star fish prevents mussels down the shore.

Is this true? Maybe the mussels are limited by abiotic factors. He investigated this by doing a manipulation - what did he do and find?

Answer 55

He removed the star fish.
The mussels moved down.
He added back in the star fish.
The mussels went back to how they were.

The study found predation determines distribution too.

Question 56

General paradigm (A general paradigm is a broadly accepted way of thinking or understanding within a field or discipline):

What are the general paradigm beliefs of Paine (1974)?

Answer 56

• Physiological constraints control upper limits.
  -Biotic factors control lower limits

except
-Pelvetia canaliculata (channelled wrack (seaweed))
-Balanus glandula (acorn barnacle)

Question 57

Interaction between environmental gradients (e.g. shore height and wave exposure).
Figure: Raffaelli & Hawkins (1999)
Zonation was seen on ___________shores.

Answer 57

sheltered

Question 58

In niche performance curves, where the two species performance curves overlap shows what?

Answer 58

Where these species overlap and can possibly live is where we see biotic interaction e.g. competition.
One will have to outcompete the other.

The dotted line in the middle of the species overlap:
Below dotted line - Species A dominates
Above the dotted line - Species B dominates.
Abiotic factors determine the outcome of the biotic factors.

Question 59

What is a fundamental 1-dimensional niche for a species?

Answer 59

Is the specific range of environmental conditions along a single factor (like temperature or humidity) where the species can survive and reproduce without competition from other species.

Question 60

How does temperature affect a fundamental 1D niche for a species?

Answer 60

Interspecific variation in the impact of rising temperatures.

If ‘ecological performance’ were to represent e.g. competitive ability, an increase in temperature from x to y (where the performance window of both species overlap) would result in a shift in competitive dominance between species.

Significant because abiotic factors can change over time. Even though an abiotic factor e.g. change in climate may not directly impact distribution of an organism, it may change an organisms interaction with other species.

Question 61

Paine 1974 - Predation: Pisaster limits down shore extension of Mytilus.

Mimicking climate change, what happens to species as we increase temperature?
What was found?

Answer 61

Found the height on the shore that the mussels and barnacles could grow declined, the upper zone declined as the temperature increased.

The star fish was unaffected by temperature, the foraging behaviour across the temp gradient didn’t change.

This means the predator free space for the mussel and barnacles was becoming pinched/pressed and it got warmer.

So as it was getting warmer biodiversity was decreasing as the barnacle mussel zone was slowly shrinking.