Challenge 3 - Sustainable harvesting

Question 1

what is sustainable harvesting?

Answer 1

the largest amount of harvest activity that can occur without degrading the productivity of the stock

Question 2

what are the 5 important points to note when thinking about sustainably harvesting?

Answer 2

>population size
>precision of population estimate
> rate of population increase
> rate of harvesting
>ethics

Question 3

how do you measure population size?

Answer 3

> distribution
abundance
density
dispersion

Question 4

what is distribution?

Answer 4

(where are things?)
> dimensionless
> important for conservation, disease

Question 5

what are the types of dispersion?

Answer 5

> how clumped are the organisms?

clumped, random and uniform

Question 6

what is abundance?

Answer 6

(how many things are there?)
> important for conservation, species management, disease.
> needed in conjunction with distribution

Question 7

what is density?

Answer 7

> qualification of abundance taking into consideration dispersion

Question 8

how do you estimate changes in population size? (formula)

Answer 8

future population size = current size + #births - #deaths

>ignoring any arrivals or departures from/to other population

Question 9

what affects both births and deaths?

Answer 9

> demography
survivorship
life history strategies

Question 10

what is demography?

Answer 10

age and sex structure will influence population growth of the next generation

Question 11

what is survivorship?

Answer 11

> % chance of offspring getting to breeding age,
chances of survival can differ dramatically among different species,
some suffer most of their mortality early in life, others later

Question 12

what is life histories

Answer 12

> description of when an organisms reproduces
how many offspring it makes
how much investment in offspring
how many times it reproduces

Question 13

what are the what is the size number trade off?

Answer 13

you can either have less energy (small size) per offspring and make more offspring, or you can have more energy (large size) per offspring and have less offspring

Question 14

what are two examples of animals with differing size-number ratios of offspring?

Answer 14

salmon = 1 million eggs, little investment per offspring
kiwi = 1 egg, every bit of investment

Question 15

what are the two different types of parental care?

Answer 15

semelparity vs iteroparity

Question 16

what is semelparity?

Answer 16

semelparity is big investment either in quality or number of offspring (northern quoll)

Question 17

what is iteroparity?

Answer 17

iteroparity is less of an investment per round but more rounds

Question 18

what are some other factors that are important for generation time?

Answer 18

> offspring size / parental care

> age at reproduction/ generation time

Question 19

what are the pros of being semelparous?

Answer 19

> doubts /low probability about making it to the next cycle
worthwhile breeding now while you can
increasing amount of offspring

Question 20

what is rMAX?

Answer 20

the maximum population growth (constant)

Question 21

describe exponential population growth

Answer 21

> it has a lag time for the first few generations
then the growth is exponential.
the formula is dN/dt = rmax x N (population size)
species that follow this type of growth curve are called r type species
bacteria, cane toads, flies
also called opportunistic species

Question 22

describe logistic population growth

Answer 22

> small lag
exponential growth at first
deceleration
then a stable equilibrium
formula is dN/dt = rmax x N[(K-N)/N]
where k is the carrying capacity
K could be # of predators, # of resources
species that follow this curve are called k type species
also called equilibrial species
also has a point of maximum growth, which has the steepest gradient.

Question 23

describe a thermal dependance curve

Answer 23

> has a critical thermal minimum (CTmin), i.e., the lowest temperature an animal an survive in
CT max
Topt (optimum temperature for fitness
Pmax (performance at Topt)

Question 24

know the difference between a thermal dependance curve in a temperate environment and a tropical environment.

Answer 24

also know climate change will affect these distributions and the organisms that live in those bounds

Question 25

what is an ecological niche?

Answer 25

> an organism’s “fit” to the environment
each organism relies on a unique mix of resources
each organism is compatible with a set of environmental conditions

Question 26

what is a fundamental niche?

Answer 26

> the theoretical conditions a species can survive in
where they CAN live
factors include: temperature, salinity, moisture ranges

Question 27

what is a realised niche?

Answer 27

> subset of fundamental niche
restrained because of species interactions
the environments where a species DOES live
competition with other species for resources determines realised niche.

Question 28

what are the characteristics of an equilibrial species?

Answer 28

> stable environments
> reproduce late
> live for a long time
> low mortality rate
> iteroparous
> high investment in a few offspring (not necessarily)
> often extensive parental care
> often follow K species curves

Question 29

what are the characteristics of opportunistic species?

Answer 29

> hugely variable environment / many disturbances
reproduce early in life cycle
live fast, die young
high mortality rate
semelparous
low investment in each offspring but lots of offspring
little to no parental care
R species
these species are more suited to urbanisation.
lots of young that mature quickly then breed and reproduce quickly

Question 30

what environments select for each type of life history (K and R)

Answer 30

> frequent environmental disturbance can select for opportunistic life histories
lawn mower = advantage for opportunistic life histories

Question 31

what regulates intrinsic population growth?

Answer 31

Density dependent factors (negative)
>competition 
>predation
Density independent factors
>climate
> seasonal change in temp
> carrying capacity

Question 32

how does predation affect intrinsic growth rate?

Answer 32

> in the presence of different predators, tadpoles (and other animals) can express different phenotypes then each other and from a control
in tadpoles in the same enclosure as fish, they had a much smaller tail, letting then swim faster to escape death
in tadpoles in the same enclosure as beetles (that act in the same way as dragonfly larvae) they had a much larger tail, this is so that some of the flesh is expendable, and their vitals are protected.

Question 33

how does competition affect intrinsic growth rate?

Answer 33

> resources are limited at a local scale
as density increase, ratio of consumer to resources increases
as density of population increases, growth rate decreases, as less food available.
also tadpoles can secrete growth inhibiting hormones to those round them.
in barnacles, higher competition meant that they were smaller and invested less resources into reproduction, so offspring smaller than in barnacles with less competition (gonad size)