Lab 4

Question 1

sympatric distribution

Answer 1

Resources ( e.g., light, water, food, shelter) in the environment are limited, and species can only exist in the same habitat if they exploit different resources

Question 2

Allopatric or parapatric distribution

Answer 2

Resources ( e.g., light, water, food, shelter) in the environment are limited, and species can only exist in the same habitat if they inhabit different physical locations

Question 3

niche

Answer 3

The resources and conditions that an organism requires to survive and reproduce.

The niche concept in ecology refers to the existence of a species in a particular place with a specific biotic community

Question 4

Space available for a stable or growing population is dependent on the conditions of _____ and ____

Answer 4

the particular location (the abiotic or environmental factors)

and

the other organisms in the community (biotic factors)

• Changes to abiotic conditions (such as pollution from cars ) can make previously habitable niches uninhabitable.

Question 5

fundamental niche

Answer 5

The area where an organism can theoretically exist, based on its abiotic requirements.

However, species do not occupy their entire fundamental niche. Sometimes a second competing species requiring some of the same resources is present and restricts the first species to a narrower range of environmental conditions or resources.

Question 6

realized niche

Answer 6

The proportion of the fundamental niche which is actually occupied by a species.

Question 7

Competition

Answer 7

In an ecological context, refers to the interaction of two or more organisms striving for the same limited resource and the results are mutually detrimental to all of the competing organisms.

Competition is one factor that might determine the size of the realized niche , affecting where organisms occur and how they adapt to their environment.

Even species that are non-motile can compete through various adaptations such as faster growth to over grow adjacent organisms, excretion of toxic chemicals into the environment and being better at accessing nutrients and water.

Question 8

specialist species

Answer 8

Exploits a relatively narrow range of the resource and thus can be referred to as a specialist species with regards to a resource.

Question 9

generalist species

Answer 9

exploits a broader range of the same resource

Question 10

niche overlap

Answer 10

when diff species use the same resources.

Question 11

competitive exclusion

Answer 11

When two species compete for a limited resource, one of the species may eventually displace or eliminate the other from the habitat where their distributions overlap.

Critical resources such as food, water, space, sunlight, etc. are of primary importance.

Question 12

Three outcomes of competitive exclusion are possible at the species level:

Answer 12

1. One species replaces another throughout the entire geographic range of the competitively inferior species, resulting in its extinction.
2. One species eliminates another from part of its range, resulting in a non- overlapping (allopatric or parapatric) distribution.
3. Both species remain sympatric, but the competitively superior species forces the less efficient or less aggressive species to abandon use of the limited resource and replace it with an alternative.

Question 13

Tree bark

Answer 13

is a common substrate for lichens, and different species and ages of trees vary in the texture, moisture-holding capacity, and chemistry which can lead to differences in both the species that colonizes a particular tree bark substrate and the succession of lichens that follow

Question 14

One of the fundamental goals of ecology

Answer 14

is to explain the processes that determine different species diversity or patterns of community structure.

However, any hypothesis about cause- effect relationships must be based on sound descriptions of the patterns.

Question 15

objective of your first project

Answer 15

Examine and describe patterns that exist with regard to urban lichen communities and attempt to identify relationships between the occurrence of these communities (or biotic factors) and the characteristics of the physical environments in which they are found (abiotic factors).

Examining lichen communities from city trees, and whether these communities differ, in composition or abundance, based on habitat type and environmental factors.

In our field study, each quadrat would constitute a sampling unit. Therefore, in this and many experiments you will be using your own data combined with data collected by your classmates to increase your sample size. Together these sampling units will constitute your “sample” of the statistical population.

Question 16

community

Answer 16

can be described by the different species present or species composition , their distribution, and their abundance in the environment.

Question 17

Most reliable estimate of abundance is obtained from direct counts.

Answer 17

When counts are obtained from a sampling unit of known size (a plot or a quadrat) they may be converted directly to absolute density, the number of individuals per unit area, and then they may be converted to any of several indices developed by ecologists to compare species composition.

Question 18

species richness

Answer 18

Total number of species present in each area.

The simplest method of comparing between two communities is to carry out direct counts and then calculate species richness.

However, two areas with the same species richness may be very different ecologically.

Question 19

speices richness example

Answer 19

a quadrat with five individuals of each of five species (even Community) has the same species richness (five) as one with 21 individuals of one species and one each of four other species (uneven community).

Evenness ranges from perfectly even (=1) to perfectly uneven (=0).

Each quadrat may each contain unique species, and thus may additionally differ in actual species present (species composition).

Question 20

species diversity

Answer 20

A measure that incorporates both the number of species present (richness) and their relative abundances (evenness).

More comprehensive method of comparing communities

Although this method takes into account more details than species richness, it does not consider species composition, which will differ based on habitat conditions.

A community has high species diversity if many equally abundant species are present.

If a community is composed of very few species, or if only a few species are abundant, then species diversity is low.

High Simpson’s reciprocal or Shannon species diversity indicates a highly complex community, as a greater variety of species allows for a larger array of species interactions.

Question 21

Shannon Diversity Index ( H’),

Answer 21

The most commonly used formula for calculating species diversity.

H’ has a minimum value of 0, and increases as the number of species (richness) and the proportion of the total that occurs in each species (evenness) increases.

Where pi is the proportion of the ith species, and log e is the natural log of pi , and s is the number of species in the community.

This number can be thought of as the uncertainty of predicting the species randomly picked.

In a community of all the same species there is 0 chance of picking something different.

Question 22

Simpson’s Reciprocal Index (D_s)

Answer 22

Also known as Effective Number of Species or Hill’s Index.

One of the most straightforward formulas for calculating species diversity.

the inverse of Simpson’s index, and considers not only the number of species (richness) and the total number of individuals in an area, but also the proportion of the total that occurs in each species (evenness).

Where ni is the number of individuals of species i, and N is the total number of individuals of all species in the quadrat.

This number can be thought of as the number of equally common species required to cause the observed variability in the sample

Question 23

community stability

Answer 23

the ability of a community to be unaffected by disturbance.

Question 24

random sample

Answer 24

Is one in which every member of the statistical population (every individual organism or every point of ground, for example) has an equal and independent probability of being included.

Comments on individual samples are rarely meaningful unless they are used to illustrate variation.

Are more likely to be independent and unbiased which is a prerequisite for many statistical tests.

To be representative, our sample must be adequate in size = will accurately reflect the statistical population mean and variability.

Question 25

systematic samples

Answer 25

involves a sampling method that has some sort of systematic or regular arrangement, e.g., sample plots may be located every 100 meters, or every third person may be interviewed.

Advantage of systematic sampling is that it is usually simpler than random sampling.

Question 26

One common method of systematic sampling used in ecological field studies are transects.

Answer 26

Many types of transects techniques (i.e., belt transects, line transects, strip transects), but for the most part they involve some sort of straight line(s) of a set distance going through the study area and sampling occurs at predetermined intervals along the transect line.

Question 27

quadrat sampling

Answer 27

Where individuals within a known area are identified and counted.

Can be random or systematic.

Question 28

Sample, Sample unit, Sample size

Answer 28

a sample is a representative subset of the statistical population being studied.

a sample unit is a single measurement of that sample. So multiple sample units make up the complete sample.

EX: be a single quadrat of vegetation, or a single aquatic quadrat, and many quadrats are then assessed to make up a single sample that represents the population. If the sample unit is from a treatment in an experiment, it may be referred to as an experimental unit.

Sample size, therefore, is the number of sampling unit s that make up a sample.

• the larger the sample size , the more likely it is to be adequate.
• large sample made up of small- or medium -sized sampling units is better than a small sample of large sized sampling units, since the former gives a better picture of the variation within the population being sampled.

Question 29

Replicate

Answer 29

is a sampling unit where there is the independent repetition of treatment conditions exactly.

EX: This could be a vegetation or aquatic quadrat, if that quadrat is independent of others tested, or it could be a single lab experimental setup that is repeated numerous times under the same conditions.

If an experiment is well designed, sampling unit s and replicates are one and the same.

Question 30

Population Vs Sample

Answer 30

sample mean (x ̅ ), sample variance (s² ), and sample standard deviation (s) are the estimates of the population’s true values–

the population mean ( μ ), population variance (σ² ), and population standard deviation (σ).

Population values include all possible samples that could be taken, whereas the sample is the number of measurements that a researcher has time and resources to measure for a given study.

Question 31

Confidence intervals

Answer 31

Give an estimate of the values that are most likely (95% likely, usually) to contain our true population mean.

In other words, our 95% confidence interval gives us the range in which our population mean is 95% likely to occur, based on our collected sample values.

This estimate is a useful measure of how variable our sample is.

The more variable the sample, the larger range of possible values for the population mean.

A smaller confidence interval implies an estimate closer to the population mean.