Lesson 5 - Populations and communities

What is speciation?

What is speciation?

The formation of new species

Why is it important to Estimate the size of a population?

better understand:

• ecological health of an area

• how to direct conservation efforts

• How to assess the effects of conservation efforts

• The impact of human activity

What some random sampling techniques can be used to estimate the size of a population?

• simple

• convenience

• systematic

• cluster

• stratified

What population estimation technique do we use for motile species?

mark + release

How does the mark and release technique work (step 1)?

• divide habitat into more manageable sections

• can be done using a grid system with GPS coordinates or assigning letters to columns and numbers to rows

• use a random coordinates generator

How does the mark and release technique work (step 2)?

• capture and mark a significant sample of the population

• allow marked organisms to fully reintegrate

• capture a second sample of the population

• count and record the number of marked + unmarked individuals

What is the equation called for estimating motile populations?

lincoln index

What is the lincoln index equation?

population size estimate = no. of individuals in first sample ×(no. of individuals in second sample/number of recaptured individuals already marked)

What are some assumptions of the mark and release method?

• the marking technique does not have any influence on the behaviour/survival of organisms

• the marked individuals fully reintegrate into population and have equal chances of being captures compared to unmarked individuals.

• no births, deaths, immigrations/emigrations during study period

what are some ethical and effectiveness considerations related to the mark and release method?

• avoid injury/death, habitat damage

• could mark be washed off?

• can marks be removed after study?

• avoid making it visible to predators

• does not affect sexual attractiveness

what method do we use for sampling sessile organisms?

Quadrat sampling

How does quadrant sampling work?

randomly placing quadrats and counting how many of an organism is in it.

What is the equation for estimated population size using quadrat sampling?

Estimated Population Size  = mean count per quadrat x  total area (m²)/area of each quadrat (m²)

Name part 1

slow growth

Name part 2

rapid growth

Name part 3

stable state no growth

Describe what is happening at part 1 slow growth

A small number of individuals reproduce. BR is higher than DR

Describe what is happening at part 2 rapid growth

ever-increasing number of  individuals reproduce exponentially (no constraints on population size)

Describe what is happening at part 3 stable state

(reached carrying capacity) Population declines until it remains stable with cyclic fluctuations. BR=DR

What is carrying capacity?

the maximum population size that a given environment can sustain over a certain period of time. 

What are some factors that can influence the carrying capacity?

food, shelter, light and competition

What are the density dependent factors?

Predators, availability of resources, nutrient supply, disease, accumumlation of wastes.

What are the density independent factors?

phenomena (natural disasters), abiotic factors, weather condition

What do density dependent factors do to populations?

keep populations at or below carrying capacity.

Explain the negative feedback cycle using this image.

Is exponential population growth possible in natural environments?

no

why is exponential population growth not possible in natural environments?

there will eventually be a limiting factor like depletion of resources

What is sigmoidal growth?

a modification of exponential growth in which the percent change gets smaller as the population approaches the carrying capacity.

What is competition?

the struggle between organisms to survive as they attempt to use the same limited resources

What is intraspecific competition?

Individuals competing for resources who are the same species.

What is interspecific competition?

Individuals competing for resources who are of different species.

Explain the negative feedback cycle of intraspecific competition using the diagram

1. Lots of resources, all organisms have enough to survive and reproduce – population size increases

2. Resources now limited, not enough for all to survive, population decreases in size

3. Smaller population means less competition, can survive and reproduce. Population grows

What is intraspecifc co-operation?

members of a species work together to aid survival of a group

What are the four symbiotic relationships?

• mutualism

• commensalism

• parasitism

• Pathogenicity

What is mutualism?

all species involved benefit from their interactions.

What is commensalism?

one species benefits without causing harm to the other

what is parasitism?

one species benefits at the expense of the other.

what is pathogenicity?

pathogens invade and multiply is host disrupting normal physiological functions.

What is the difference between pathogenicity and parasitism?

pathogens have direct + immediate effects and can spread easily between hosts.

Give one example of where humans have introduced non-native species to another environment?

Rats on to the Pacific islands by Chinese merchant ships.

What are non-native species?

introduced by humans

what are native species?

naturally occurring species (no human intervention)

What are invasive species?

non-native species that causes harm

What are the impacts of invasive species using lion dish as an example?

Lionfish do not have any predators. They directly feed on smaller fish removing prey for native fish.

what can cause invasive species?

trade and transportation

What is the main impact of invasive species in the new environment?

high efficiency when using resources so they reproduce rapidly outcompeting other species to extinction?

What are the different testing methods for assessing the presence of interspecific competition?

• laboratory experiment

• field observations

• removal of species to monitor response of remaining organisms

What is top-down control of populations?

the abundance of lower trophic levels in a food chain is regulated by organisms at higher trophic levels.

What is bottom-up control of populations?

when the availability of resources at lower trophic levels influences the abundance of organisms at higher trophic levels. 

What is allelopathy?

release of biochemicals which prevent survival of neighbouring organisms

What do some trees secrete to deter potential competitors?

allelopathy and antibiotic secretion

What is one example of allelopathy?

black walnut: releases juglone which inhibits growth and function of nearby plants.