Lesson 5: Populations and communities

Question 1

What is a population?

Answer 1

A group of the same species that interbreed and share a gene pool.

Question 2

Why estimate population size?

Answer 2

To assess ecological health, guide conservation, and evaluate human impact.

Question 3

What is random sampling?

Answer 3

Unbiased selection of organisms to get a representative sample.

Question 4

What is the Lincoln Index?

Answer 4

N = (M x C)/R
M = Number of individuals marked and released initially
**C **= Total number of individuals captured in the second sample
**R **= Number of recaptured marked individuals in the second sample

Question 5

What is carrying capacity?

Answer 5

The max population size an environment can sustain.

Question 6

What are density-dependent factors?

Answer 6

Factors like competition, predation, and disease that depend on population density.

Question 7

What are density-independent factors?

Answer 7

Factors like natural disasters or human activities that affect populations regardless of density.

Question 8

Exponential vs. sigmoidal growth?

Answer 8

Exponential: unlimited resources, rapid growth. Sigmoidal: limited resources, stabilizes at carrying capacity.

Question 9

What is intraspecific competition?

Answer 9

Competition between individuals of the same species for resources.

Question 10

What is interspecific competition?

Answer 10

Competition between different species for the same resources.

Question 11

What is mutualism?

Answer 11

A symbiotic relationship where both species benefit.

Question 12

What is commensalism?

Answer 12

One species benefits, the other is unaffected.

Question 13

What is parasitism?

Answer 13

One species benefits at the expense of the other (host).

Question 14

What is an invasive species?

Answer 14

A non-native species that harms native ecosystems.

Question 15

What is top-down control?

Answer 15

Predators regulate populations at lower trophic levels.

Question 16

What is bottom-up control?

Answer 16

Resource availability at lower trophic levels influences higher levels.

Question 17

What is allelopathy?

Answer 17

Release of chemicals to inhibit competitors’ growth.

Question 18

What is the chi-squared test used for?

Answer 18

To test for associations between categorical variables.

Question 19

What are the assumptions of the Lincoln Index?

Answer 19

Marking doesn’t affect behavior, marked individuals reintegrate, no population changes during study.

Question 20

Sessile vs. motile organisms?

Answer 20

Sessile: don’t move (e.g., plants). Motile: can move (e.g., animals).

Question 21

How is quadrat sampling used to estimate population size for sessile organisms?

Answer 21

Quadrats are randomly placed in a habitat, and organisms within them are counted to estimate the total population.

Question 22

What is the capture-mark-release-recapture method?

Answer 22

A method to estimate motile population size by capturing, marking, releasing, and recapturing individuals, using the Lincoln Index.

Question 23

Why does population growth slow as carrying capacity is reached?

Answer 23

Resources become limited, leading to increased competition, higher mortality, and reduced reproduction.

Question 24

What is a community in ecological terms?

Answer 24

A group of populations living and interacting in a particular area.

Question 25

Give examples of herbivory, predation, competition, parasitism, pathogenicity, and mutualism.

Answer 25

Herbivory: deer eating plants. Predation: lion hunting zebra. Competition: squirrels fighting for nuts. Parasitism: ticks on dogs. Pathogenicity: bacteria causing disease. Mutualism: bees pollinating flowers.

Question 26

How do invasive species impact endemic species?

Answer 26

They outcompete, prey on, or introduce diseases to native species, often leading to population declines or extinction.

Question 27

How do humans contribute to the spread of invasive species?

Answer 27

Through trade, transportation, accidental releases, and intentional introductions.

Question 28

What is the chi-squared test used for in ecology?

Answer 28

To determine if there is a significant association between two categorical variables, such as species presence.

Question 29

How do you interpret chi-squared test results?

Answer 29

If the calculated value exceeds the critical value, there is a significant association between the variables.

Question 30

What are the limitations of the chi-squared test?

Answer 30

It assumes large sample sizes and is not valid for non-categorical data.

Question 31

How do predator-prey interactions influence population dynamics?

Answer 31

Predators regulate prey populations, preventing overpopulation, while prey availability affects predator survival.

Question 32

What is top-down control in population regulation?

Answer 32

Predators at the top of the food chain control the abundance of species at lower trophic levels.

Question 33

What is bottom-up control in population regulation?

Answer 33

Resource availability at lower trophic levels (e.g., plants) influences the abundance of higher trophic levels (e.g., herbivores, predators).

Question 34

Compare allelopathy and antibiotic secretion.

Answer 34

Allelopathy: plants release chemicals to inhibit competitors. Antibiotic secretion: bacteria release chemicals to kill or inhibit other bacteria.

Question 35

How does allelopathy give competitive advantage?

Answer 35

It reduces competition by suppressing the growth of nearby organisms.

Question 36

How does antibiotic secretion give competitive advantage?

Answer 36

It kills or inhibits competing bacteria, allowing the secreting bacteria to thrive.

Question 37

What is the ecological significance of mutualism?

Answer 37

It enhances survival and reproduction for both species, promoting ecosystem stability and biodiversity.

Question 38

What is the ecological significance of parasitism?

Answer 38

It regulates host populations and can influence community structure and ecosystem dynamics.

Question 39

What is the ecological significance of predation?

Answer 39

It controls prey populations, maintains biodiversity, and influences energy flow in ecosystems.

Question 40

What is the ecological significance of competition?

Answer 40

It drives natural selection, resource partitioning, and species adaptation.

Question 41

What is the ecological significance of herbivory?

Answer 41

It influences plant populations, nutrient cycling, and energy transfer in ecosystems.

Question 42

What is the ecological significance of pathogenicity?

Answer 42

It regulates host populations and can lead to evolutionary adaptations in both hosts and pathogens.