Conservation Science Chapter 8

What are the three main questions (according to your textbook) that relate to the urgency of conservation plans for a population (or a species)?

The three main questions are: 1) How many individuals are in the population? 2) What is the trend in the population size over time? 3) What is the likelyhood of extincition.

What are some of the reasons (we covered three in lecture) why it is generally difficult to obtain an estimate of the number of individuals in a population for most species?

1) expensive 2) time consuming 3) scientifically challenginly

Be able to explain the quadrat method for estimating the population size for a species.

For what kind of species is this method most useful?

The quadrat method is most useful for sessile or slow-moving species, such as plants or certain marine organisms. It involves laying down square plots in a habitat to sample and estimate population density based on counts within these designated areas (transects).

Be able to provide (or at least recognize) some examples of methods for estimating the relative abundance of animal populations.

What are some examples of signs that surveyors can use as evidence of an animal’s presence?

How does “unit of effort” play into assessing relative abundances?

Relative abundance is the number of individuals spotted or trapped, standardized “per unit of effort.”

• Poop, footprints, and other signs of the animal.

• unit of effort is the area you are measuring.

Be able to explain the mark-recapture technique for estimating the population size for a species. N=MS/r

Mark-recapture techniques (e.g., Lincoln-Petersen) can be used to estimate population sizes of mobile animals

6 assumptions of marked-recaptured method

1. Marking does not affect survival of individuals.

2. Marking does not affect probability of recapture.

3. Upon release, marked individuals mix with entire population

4. Captured individuals are representative of the whole population.

5. The population is closed and stable.

6. The marks are not lost.

In very general terms, why/how can estimates of a population’s genetic diversity be used as an indication of past population sizes of that species?

Genetic diversity reflects how many different gene variants exist in a population. Genetic diversity reflects past population sizes primarily through the effects of genetic drift.

Be able to recognize, understand, and apply the discrete time model of exponential change in a population size.

o   Make sure to memorize the simple formula.

o   Understand what lambda (λ) represents in this model.

Used to estimate population trends

• Nt+1 = Lamba * Nt

• Lamba = population growth rate

  • λ = Nt+1 / Nt

Be able to interpret a life-cycle diagram for a species.

illuminate what measures are needed to produce a more realistic population model

PVA

Population Variability Assesment: a quantitative assessment of the probability that a population will become extinct during some specified time horizon

MVP

Minimum Viable Population: a population size above which a species has a good chance of surviving over some specified time horizon