C 4.1Populations & Communities

Question 1

what do populations form?

Answer 1

it forms an important group

by interacting with other populations within a community.

Question 2

What distinguishes a population of a speicies?

Answer 2

Reproductive Isolation- is when different species or groups cannot mate or produce offspring, which helps create new species.

Question 3

What is the reason for estimating population size

Answer 3

It would be impossible to count all the individual organisms of a population in a habitat by hand. Instead, we count a sample from a small area and multiply this by the total area of the habitat. This gives an estimate of the total population.

Question 4

What is the need for Randomness for sampling producers?

Answer 4

To remove any uncounicous bias

It important to ensure that the data collected is unbiased, representative, and reliable

Question 5

What are two common sampling methods for sessile organism:

Answer 5

Quadrat Sampling-
and
Line or Belt transects-

Question 6

What is the Quadrat sampling

This method is only suitable for what

Answer 6

It is a method used to take a measurement of an area without systematically deciding where to take it

It eliminates bias which may influence your measurements.

This method can be used with quadrats when working out the population size of a species of stationary animals or plants

This method is only suitable to sample sessile organisms like plants or very small, small moving animals

Question 7

When do you use the Capture–mark–release–recapture

When do you use the Lincoln index

Answer 7

Capture–mark–release–recapture

method of estimating population size (N) of mobile animals

A sample of animals is captured, marked, and released back into their habitat. Later, another sample is captured, and the number of marked individuals is recorded.

Lincoln index

is a mathematical formula used in the capture-mark-recapture method to estimate population size.

Question 8

What is standard deviation

Answer 8

Standard deviation is a measure of how spread out data values are from the mean

A low standard deviation means most values are close to the mean, while a high standard deviation indicates greater variation

Question 9

examples of resources that animals would compete for

Answer 9

Space
water
nutrients
mating partners
Sheleter
territory

Question 10

examples of resources that plants would compete for

Answer 10

Space
water
nutrients
light
CO2
Tempreture
Soil

Question 11

Definintion of Carrying capacity and some examples

Answer 11

Carrying capacity is the largest number of animals or plants that a place can support without running out of food, water, or space. If too many live there, they compete for resources, and some may not survive.

Question 12

3 Carrying capacity some examples
D
F
B

Answer 12

Deer in a Forest – A forest may support 500 deer based on available food and water. If the population grows beyond this, food shortages and competition occur, reducing the population.

Fish in a Pond – A pond with limited oxygen and food can only sustain a certain number of fish before competition leads to deaths or migration.

Bacteria in a Petri Dish – Bacteria grow rapidly but eventually stop due to limited nutrients and space, reaching their carrying capacity.

Question 13

What are density dependent factors

examples

Answer 13

are environmental factors that affect a population more as its size increases

Food and water availability
Space for territories & next
Availability of mates
Diseases
Predation

Question 14

What are density independent

examples

Answer 14

are environmental conditions that affect a population regardless of its size

Environmental change
Build-up of toxic by products of metabolism
Injury
Senescence (death from age related illnesses)
Human Activities
Droughts & Water Shortages

Question 15

Population size can be limited by what

Answer 15

by density dependent and density independent factors

Question 16

What are density dependent factors?

Examples

Answer 16

Factors that depend on population size, e.g. competition, predation, food, disease, and parasitism

Question 17

What are Density independent factors?

Examples

Answer 17

Factors that affect all populations in a similar way, regardless the of population size, e.g. drought, wild fire, volcanic eruptions, hurricane, deforestation…

Question 18

What pushes the population back to its capacity?

Answer 18

density dependent factors as these factors regulate population growth by increasing death rates, lowering birth rates, or encouraging migration.

Question 19

Competition for limited resources (killing) causes what 2 things

Answer 19

Increased risk of predation

Transfer of pathogens and diseases and pests in dense popultaions

Question 20

What are the three main groups of density dependent factors

Answer 20

Competition
Predation
Disease,Parasitism,Infestation

Question 21

How does the density of a population affect competition

Answer 21

A higher number of individuals, lower the amount of available resoruces so competition will increase

Question 22

How does the density of a population intensify predation?

Answer 22

a higher population density = more intense predation

Question 23

How does the density of the population affect the spread of disease & pathogens?

Answer 23

a higher population density = a higher chance of spreading diseases and pest

Question 24

What is a negative feedback loop

Answer 24

It is a self-regulating system that keeps things balanced by correcting any changes to maintain stability.

Question 25

What does Population growth follows and how does it look like

Answer 25

a sigmoidal curve- S-shaped graph that shows how a number changes over time, often seen in population growth or biological processes. It starts with slow growth, then enters a rapid increase phase, and finally levels off when it reaches a limit, such as carrying capacity.

Question 26

What are the three stages of the sigmoidal curve

Answer 26

Exponential Transition Plateau

Question 27

What is the Exponential stage

Answer 27

It is the rapid increase because there are still plenty of supplies and resoruces Meaning that limiting factors are lower and therefore they increase more as there isn't much stopping them and also less competition

Question 28

What is the Transition stage

Answer 28

Population growth is slower the limiting factors are now increasing and now less resources are avaliable making population size decrease More competition= more killing= less population

Question 29

What is the Plateu stage

Answer 29

Reaches its limit of carrying capacity There is no more population increase becasue the limiting factors are high and more competion and survial decreases

Question 30

What are the four main factors that affect population do they increase or decrease population

Answer 30

immigration (+) increases from external population coming in mortality (-) decreases population due to death emigration (-) decreases population as result of loss of external population natality (+) increases population due to reproduction

Question 31

I+N>E+M= what does it result and how will the graph look like

Answer 31

More population growth graph going up

Question 32

I+N=E+M= what does it result and how will the graph look like

Answer 32

Stable population growth Graph going up and down

Question 33

I+N

Answer 33

Less population growth Graph going down

Question 34

Reasons for the exponetial phase/growth

Answer 34

Abundant Resources Low Competition High Birth Rates Favorable Environmental Conditions Genetic Adaptation & Fitness Lack of Limiting Factors

Question 35

Case study about the Population growth curves: bearded vultures background: Population Growth Stages (Sigmoidal Curve):

Answer 35

Since 1986, bearded vultures have been released in the Alps as part of an international conservation project. The first release in Swiss National Park occurred in 1991. Lag Phase: Early releases from 1991 to 2007 (26 captive-bred vultures). Slow initial growth as birds adapt to the environment. Exponential Growth Phase: Many of the released vultures survived and bred in the wild. Natural broods began occurring in Engadine and the Swiss-Italian border. Population increased rapidly as survival and reproduction improved. Stationary Phase: As population stabilized, no further releases were planned in the National Park. The ecosystem now supports natural breeding without human intervention.

Question 36

Modelling of the sigmoid population growth curve in Duckweed

Answer 36

Place a small number of plants in a container, e.g. a plastic cup Count the number of fronds (leaves) every day until the surface of the container is covered, i.e. the population has ceased to increase. Plot your results – you should obtain a sigmoidal curve

Question 37

Reasons for intraspecific competiton within a population

Answer 37

Limited Food Supply – Water Shortages – Space & Shelter – Mates & Reproduction – Light & Nutrients (for Plants) – Dominance & Social Hierarchy – Carrying Capacity Limits –

Question 38

Examples of intraspecific competiton

Answer 38

Lions Fighting for Territory – Male lions compete for dominance and access to a pride, ensuring they get to mate and protect their area. Trees Competing for Sunlight – In a dense forest, taller trees block sunlight from smaller ones, forcing them to grow taller or adapt to low light conditions. Deer Fighting for Mates – Male deer (stags) compete by locking antlers in battles to win access to females during mating season. Birds Competing for Nesting Spots – Birds of the same species may fight over the best places to build nests and raise their young.

Question 39

what is intraspecific competiton

Answer 39

Intraspecific competition is when members of the same species compete for the same resources, like food, water, space, or mates. This happens because they have similar needs and live in the same environment.

Question 40

What is intrespecific competiton Examples

Answer 40

is when members of the different species compete for the same resources, like food, water, space, or mates. Different spieicies of plants competing for light diffrent animals competing for shelter

Question 41

Examples of Cooperation in Animals

Answer 41

Communal Roosting (Birds & Mammals) Birds and mammals huddle together to conserve body heat, reducing energy loss. Group Hunting (Social Predation) Hunting in groups increases success in catching prey and allows sharing of food. Defense Against Predators (Bait Balls in Fish) Some species form tight groups to make it harder for predators to attack individuals. Shared Parental Care Some species share the responsibility of raising young, increasing survival rates.

Question 42

What are the 6 types of ecological interspecific interactions/ relationship

Answer 42

Herbivory Predation Interspecific Competition Mutualism Parasitism Pathogenicity

Question 43

What is Herbivory with 1 example

Answer 43

Primary consumers feeding on producers. The producer may or may not get killed. Aphids feeding on phloem sap from plants

Question 44

What is Predation with 1 example

Answer 44

One consumer species (the predator) killing and eating another consumer species (prey) Starfish eating oysters

Question 45

What is Interspecific Competition with 1 example

Answer 45

Two or more species competing for the same resource, where the use of the resource by one species reduces its availability for the other. Ivy climbing up oak trees and competing for light

Question 46

What is Mutualism with 1 example

Answer 46

Two species living in a close association, with both species benefiting from the association. Photosynthesizing zooxanthellae living in the cells of hard corals and exchanging materials with the coral

Question 47

What is Parasitism with 1 example

Answer 47

One species (the parasite) living inside, or on the outer surface of another species (the host) and obtaining food from them. The host is harmed, the parasite benefits. Ticks living on the skin of deer and feeding by sucking blood from the deer

Question 48

What is Pathogenicity with 1 example

Answer 48

One species (the pathogen) living inside another species (the host) and causing a disease in the host. Potato blight fungus (Phytophthora) infecting potato plants

Question 49

Root Nodules in Fabaceae as a example for Mutualism as an interspecific relationship Explain what are they Explain the Mutualism And say the benifit to both organisms

Answer 49

Fabacea are a large plant family including species like clover, peas, beans. Many of them have developed a mutualistic relationship with Rhizobium bacteria, which live in root nodules grown by the plant. The bacteria receives protection and sugars made by the plant through photosynthesis. Inside the nodules O2 concentration is low. In turn, Rhizobium absorbs N2 and converts this to NH4 which the plant uses for the production of proteins. This prevents plants from nitrogen deficiency The bacteria receives protection and sugars The plant is prevented from a nitrogen deficiency

Question 50

Mycorrhizae in Orchidaceae as a example for Mutualism as an interspecific relationship Explain what are they Explain the Mutualism And say the benifit to both organisms

Answer 50

The roots of most plants form an association with fungi, called mycorrhizae in soil. Then fungus absorbs nitrogen, phosphorus, fixed carbon and water from the soil and supplies them to the plant. Orchid seeds do not contain food reserve, so they need these nutrients. The orchid supplies the fungus with carbon compounds from photosynthesis

Question 51

Zooxanthellae in hard corals as a example for Mutualism as an interspecific relationship Explain what are they Explain the Mutualism And say the benifit to both organisms

Answer 51

Hard corals secrete CaCO3 to form a skeleton where the individual animals (called polyps) can live. This also provides a safe and protected environment for photosynthetic algae (zooxanthellae) close to the surface of the sea (sunlight). The algae supply the coral with glucose, amino acids and O2 from photosynthesis, while the coral provides CO2 from cellular respiration for photosynthesis to the algae.

Question 52

How does predation affect prey populations, and why do some ecosystems maintain a stable equilibrium while others experience cyclic population oscillations?

Answer 52

When a predator kills its prey, the prey population becomes one smaller. However, the prey population does not change much, because birth and death rates are at balance, as is the case with the predator population. In some communities this dynamic equilibrium is not shown and instead cyclic oscillations are observed.

Question 53

What is the four interactions of a prey-predator cycles

Answer 53

When there is an increase in prey numbers it increases food availability for predators, so predator numbers rise. A rise in predator numbers increases predation of prey, so prey numbers fall. A fall in prey numbers decreases food availability for predators, so predator numbers fall. A fall in predator numbers decreases predation of prey, so prey numbers rise.

Question 54

Within a food chain, interactions between members of different species in a community can operate in two directions:

Answer 54

Top-down Bottom-up

Question 55

What is the Top-Down

Answer 55

acts from a higher trophic level to a lower one. An increase in predator number will decrease the population size of the prey.

Question 56

What is the Bottom-Up

Answer 56

acts from a lower trophic level to a higher one. A population of producers may be limited by the number of nutrients in soil or water.

Question 57

How do some organisms use secondary metabolites in their metabolic pathways to deter potential competitors from their ecological niche, and why are these compounds not essential for cell growth or function?

Answer 57

Some organism have developed special ways as part of their metabolic pathways to prevent the potential of competitors from their ecological niche. These pathways are producing so-called “secondary metabolites” which are not essential for cell growth or its function.

Question 58

What are the two examples of secondary metabolites

Answer 58

Production of antibiotics and Allelopathy

Question 59

What is Production of antibiotics

Answer 59

is when certain microorganisms make special chemicals that kill or stop the growth of other bacteria. Many fungi produce antibiotic substances which prevent the growth of other species (e.g bacteria) by interfering with cell wall components of the bacteria, which eventually cause them to burst and die.

Question 60

What is Allelopathy with a example

Answer 60

Allelopathy is the release of chemicals as secondary metabolites or toxins by plants, which are given off into the soil to prevent nearby competitive plants to grow in the same area

Question 61

Production of antibiotics with a example

Answer 61

Penicillin Antibiotics like penicillin interfere with the production of peptidoglycan, a key component of bacterial cell walls. Without a strong cell wall, the bacteria cannot maintain their shape and structure. Water enters the bacteria due to osmotic pressure, causing the cell to swell and eventually burst (a process called lysis).

Question 62

Allelopathy with a example

Answer 62

Tree of heaven (Ailanthus altissima) is native to China but has spread as an invasive species in North America. It releases an allelopathic chemical (ailanthone) from roots and bark, which inhibits the growth of nearby plant meaning that a plant slows down or stops the growth of other plants around it

Question 63

What are Endemic spiecies

Answer 63

are plants or animals that exist only in a specific geographic location and are not naturally found elsewhere.

Question 64

What are Invasive/alien species

Answer 64

are non-native organisms introduced to a new environment, often disrupting ecosystems by outcompeting or harming native species.

Question 65

one local example to illustrate competitive advantage over endemic species in resource acquisition What is the invasive specie? what is the endemic speicie? What are the traits the invasive has that it outcompetes the endemic?

Answer 65

The red-eared slider/turtle: is an example of an invasive species that outcompetes endemic turtle species due to its competitive advantage in resource acquisition Generalist Diet: It consumes a wide range of food, including plants, insects, and small aquatic animals, giving it a survival advantage over specialized endemic species. High Reproductive Rate: It lays many eggs per season, allowing its population to grow rapidly. Aggressive Behavior: It often dominates basking and feeding areas, outcompeting native turtles for space and food. Adaptability: It thrives in various environments, including polluted and human-altered water bodies.

Question 66

How can the presence or absence of a species suggest interspecific competition, and why does this observation not necessarily prove it?

Answer 66

Interspecific competition is suggested, but not confirmed, if a species grows or survives better when another species is removed. This means that the presence of the second species might be limiting resources, but other factors could also be involved.

Question 67

What are some methods of investigation to investigate this: Interspecific competition is suggested, but not confirmed, if a species grows or survives better when another species is removed. This means that the presence of the second species might be limiting resources, but other factors could also be involved.

Answer 67

Laboratory Experiments Field Observations (Random Sampling) Field Manipulation (Species Removal)

Question 68

Give a example for the laboratory Experiments m t

Answer 68

The birch bolete mushroom (Leccinum scabrum) and birch trees example shows how laboratory studies can test positive or negative associations. Species can be grown together and apart under controlled conditions. Growth rates, nutrient uptake, and survival rates are compared. If species perform better alone, competition is present. If they grow better together, it suggests a positive association (e.g., symbiosis).

Question 69

Give a example for the Field Observations D D

Answer 69

Quadrat Sampling (random) The dandelion and daisy study uses quadrat sampling to observe if the two species tend to grow together or separately. Researchers place quadrats randomly in a habitat and count the occurrence of species within each. The Chi-Squared Test is used to analyze whether species distribution is independent or if they are associated (competition or co-occurrence). findings: If species are found together less frequently than expected, it may indicate competition limiting their coexistence.

Question 70

Give a example for the Field Manipulation (Species Removal) BH LH

Answer 70

The bell heather (Erica cinerea) and ling heather (Calluna vulgaris) study examines whether removing one species leads to an increase in the other. In a moorland ecosystem, one species can be selectively removed from test quadrats. If the remaining species grows more or increases in number, it means they were competing for the same resources, like soil nutrients. If species thrive in the absence of competitors, it indicates interspecific competition.