C4.1 - Communities and Population

Question 1

Population

Answer 1

Group of individual organisms from the same species living together in the same area.

Question 2

How can pops be recognized?

Answer 2

They often only interbreed with each other.

Question 3

What are some non-breeding interactions between a population?

Answer 3

• competition for resources
• cooperation to prevent predation

Question 4

Population size

Answer 4

the amount of individual organisms in that po p

Question 5

What are reasons random sampling is used to estimate pop size?

Answer 5

• pops can be very large and hard to count
• Spread over vast areas
• migration and camouflage

Question 6

What is an assumption made abt random sampling?

Answer 6

All individuals have an equal chance of being selected.

Question 7

What sampling error can occur in random sampling?

Answer 7

The difference between the estimate of pop size and true size of the population.

Question 8

Quadrant sampling

Answer 8

A method used to estimate the pop size for sessile organisms

Question 9

Outline the procedure of quadrant sampling:

Answer 9

1) Random coordinates are generated.
2) Quad frame is placed at the coordinates.
3) Population estimate formula (mean count per quad x area of whole site/area of one quad)

Question 10

What does a high SD indicate in a sample?

Answer 10

• high variability between individuals
• the population is clumped together

Question 11

what does a low SD indicate in a sample?

Answer 11

• low variability between individuals
• population is evenly distributed

Question 12

CMRR (قمرر) is used for;

Answer 12

Motile populations

Question 13

Outline the CMRR procedure:

Answer 13

1) As many captured from a specified area
2) Marked in a way that does not make them clear to predators.
3) Released.
4) Recaptured then the amount of marked vs unmarked individuals is counted.
5) use the lincoln index to count (initial caught + total recaught/total recaught with marks)

Question 14

What are 3 assumptions made abt the period between release and recapture:

Answer 14

• no deaths and no births
• no migrations
• marked ppl have an equal chance of being recaptured
• marks remain visible

Question 15

Carrying capacity

Answer 15

Maximum population size an environment can support

Question 16

Outline how a pop size reaches carrying capacity by a limiting factor;

Answer 16

• A resource is scarce/size too big
• competition
• individuals die
  carrying capacity reached

Question 17

Density- independent factors

Answer 17

These are factors that affect population size but are not affected by population size. (Ex: - Frost - Forest fire)

Question 18

What is the difference between D-I/D-D in terms of the way they they affect population size?

Answer 18

• D-D brings back size to carrying capacity by a negative feedback mechanism that decreases larger pops and increases smaller pops.
• D-I causes fluctuations in population size.

Question 19

What are some D-D factors and how do they increase with increasing population size?

Answer 19

• Competition for resources increase as pop size increases.
• Predation increases as pop of prey increases and decreases as pop of prey decreases.
• Spread of pathogens of pests increases with pop size since hosts are closer together.

Question 20

What are the 4 factors that effect population size?

Answer 20

• Natality: more individuals produced, pop size increases.
• Mortality; Individuals die, and pop size decreases.
• Immigration: individuals move in, pop size increases.
• Emigration: individuals leave, pop size decreases.

Question 21

Justify the exponential phase (phase 1) in a populationon size growth trend?

Answer 21

• Abundant resources.
• Natality Rate> Mortality rate
• Disease/pathogens/pests are rare.
• Immigration is more likely than emigration.

Question 22

Justify the transitional phase:

Answer 22

• The carrying capacity of the environment is reached.
• Natality R decreases
• Mortality R increases
• Natality R>Mortality R, but by a decreasing amount.

Question 22

Justify the plateau in pop size growth:

Answer 22

• Pop size was limited by a limiting factor (predation, competition due to food scarcity, disease).

Question 23

Give an example of a population size growth pattern:

Answer 23

• The collared dove population in europe increases exponentially.
• When a logarithmic scale was used on the y-axis, the points increased, indicating an exponential increase in population.
• Could be due to food abundance.

Question 24

Community

Answer 24

A group of different populations living in the same area.

Question 24

How can we experimentally model a sigmoid population growth curve? (Lemna example)

Answer 24

• Provide Duckweed with abundant resources (Water with nitrate and phosphate, bright light, high temperatures).
• Count the number of lemna at regular intervals.

Question 25

Between what is an intraspecific relationship?

Answer 25

Individual organisms of the same species.

Question 26

What are 2 examples of intraspecific relationships?

Answer 26

Competition and Cooperation

Question 27

What is the reason for intraspecific competition?

Answer 27

Members of a population have the same ecological niche and hence require the same resources.

Question 28

What are some examples of intraspecific competition?

Answer 28

• Duckweed and Light
• Gannets and nest sites on sea cliffs.
• Creosote bushes and water in a desert environment.
• Waxwings and berries in northern forests.

Question 29

What are some examples of intraspecific cooperation?

Answer 29

• Emperor penguin males huddle together to conserve body heat in the winter.
• Mackerel swim together in fast-moving ‘bait balls’’ to prevent predation.
• Chimpanzees hunt in groups to catch more prey.
• Eider duck parents take turns to care for offspring with multiple parents.

Question 30

What does an inter-specific relationship indicate?

Answer 30

Between different species in a population.

Question 31

What are interspecific relationships for species not living in close association?

Answer 31

• Herbivory (consumers eating producers) Ex: Bison eating grass
• Predation (consumer eating another consumer) Ex: anteaters eating ants
• Interspecific Competition for food
  Ex: Ivy competing with oaks.

Question 32

What are interspecific relationships for species living in close association?

Answer 32

• Mutualism (both species benefit)
  Ex: Zooxanthellae on corals
• Pathogenicity (living inside the host and causing disease) Ex: anthrax bacteria in kudu
• Parasitism (parasite lives in host and gets food from them) Ex: black ticks on white-tailed deer.

Question 33

Outline 3 interspecific mutual relationships between individual organisms:

Answer 33

• Rhizobium bacteria in legume root nodule (gets sugar and low oxygen environment, fixates N2 into NH3+).
• Mycorrhizae and Orchid plants (gets sugar and carbon compounds, absorbs water and minerals and passes them to orchid).
• Zooxanthellae and Hard Coral cells (get CO2 from aerobic respiration, give O2 and organic compounds by photosynthesis).

Question 34

Invasive species

Answer 34

Alien species to a habitat that has spread by competition.

Question 35

Endemic Species

Answer 35

Native species to a habitat.

Question 36

Explain the relationship between an invasive and endemic species:

Answer 36

• The 2 can have an overlapping ecological niche, where the endemic species’ population size is controlled by density-dependent factors. The pests/pathogens that normally control the alien species are absent in the new habitat, so they take over :(

Question 37

What is an example of an invasive species?

Answer 37

• The red lionfish are endemic to the indo-pacific but escaped from an aquarium in a hurricane and are now an invasive species in the Caribbean sea.

Question 38

What are ways to determine whether 2 species are interspecific competitors?

Answer 38

• Field Manipulation: Remove one species from an area and measure if the other increases in size or biomass.
• Lab experiment: grow species seperately or apart to see if they compete for resources.
• Random Quadrat Sampling and Chi-Squared Test.

Question 39

Outline the predator-prey cycle:

Answer 39

prey increases, more food for preds, more predators, more predation, less prey, less food for preds, less predators, less predation, more prey, and hence…

Question 40

Ex of Direct interactions between trophic levels:

Answer 40

Predators eat herbivores or herbivores producers.

Question 41

Ex of indirect interactions between trophic levels:

Answer 41

Predators increase, herbivores are eaten so they decrease, producers aren’t eaten so they increase.

Question 42

Outline Top-Down Control;

Answer 42

Predators increase/decrease, herbivores affected, producers affected, soil minerals affected

Question 43

Outline Bottom-up Control;

Answer 43

Soil minerals increase, producers increase, herbivores increase, predators increase.

Question 44

Secondary Metabolites

Answer 44

Products of metabolic pathways specific to certain taxonomic groups.

Question 45

What are 2 examples of secondary metabolites?

Answer 45

Allelopathic agents and Antibiotics

Question 46

How can a population size be controlled (in terms of C4.1.18)?

Answer 46

Targeting a metabolic pathway unique to the group.

Question 47

Antibiotics

Answer 47

Secreted by microorganisms to kill other microorganisms.

Question 48

Example of antibiotic case:

Answer 48

Penicillium fungi secrete antibiotics that weaken bacterial cell walls.

Question 49

Example of allelopathic agent case:

Answer 49

Ailanthus Altissima (tree of heaven) releases a plant-killing chemical that kills native plants.

Question 50

Allelopathic agent

Answer 50

Secreted by plants into soil to kill other plants.