Life History and Competition

life history traits

A set of co-adapted traits designed, by natural selection, to solve particular. ecological problems

evolution, trade offs, energy allocation

what is involved in life history traits?

reproduction

what is the most important ecological problem?

maximize

A species’ life history traits should __________ reproduction

r-K theory

Pianka’s Theory
• describes a continuum of life histories
• idea of trade-offs
• selected for by the environment

r species

favor lots of offspring with little parental care

K

favor few offspring with lots of parental care

C-S-R theory

grime’s theory for 3 way tradeoff in plants

competitive ability, stress tolerance, reproduction

what elements are involved in C-S-R theory?

trophic level

competition is between species of the same _______

exploitive and interference

2 mechanisms of competition

those at the same trophic level

what species use the same resources?

exploitative

competition by using up a resource

2 fish feeding of zooplankton, hawks and owls feeding on mice

examples of exploitive competition

chemical competition, overgrowth (plants), territoriality, encounters

examples of interference competition

interference competition

competition by direct action to keep away from resource

Allopathic

plants that poison neighbors

inverse

competition may cause a ________ relationship between the presence or
abundance of competing species.

competitive exclusion

What can a better competitor cause to the other in simple habitats?

gathering resources or being efficient with them

When resources are scarce, one species is almost always better at either….

select different habitat or different food

In the long run a species can adopt one of these two strategies to escape the negative effects of competition

character displacement

changing a characteristic over time to escape the effects of competition

reduces intraspecies competition for food

benefits of sexual dimorphism in weasels

intraspecific

competition within your own species

interspecies

competition with a different species

niche/resource partitioning

evolution creates specialists that reduce competition for a specific prey

reciprocal

competition is a _________ interaction

both

If 2 individuals use the same resource, ______ suffer negative effects because of its depletion

Grace & Wetzel

studied cattails to study competition

individuals deplete resource, reduces population growth rate, birth and death rates are affected

mechanisms by which resources limit population growth in intraspecific competition

K

population size where births are equal to deaths

1

value for lamda when at carrying capacity

negatively, positively

Birth rate is ________ density-dependent

Death rate is __________ density-dependent

K or lamda =1

in a graph of birth and death rate, what does the place where the lines cross represent?

R*

resource level where births and deaths are equal and lamda=1

0

what is the population growth at R*

Dave Tilman

author of the R* model

K

population size at R*

low

is it better to have a high or low R* when there is competition?

at winning specie’s R*

where do resources stabilize when 2 species compete?

factors that affect food availability other than competition, assumed b/d rates w/ no variation, ignores other species and resources, no predation

R* model assumptions

they are renewable

in competition model, what is assumed about the resources?

how much energy is left after taking out what is necessary for respiration

what is net photosynthesis?

light compensation point

point where plants just make enough sugars to stay alive

R*

what other variable is the light compensation point equivalent to in photosynthetic plants

shade tolerance and fast growing

what trade offs are often seen in trees

natural selection

Within a species, birth & death rates are agents of ____________

lower

in competition, does a higher or lower R* species win out?

territoriality

defense of space

food, resources, nesting sites, mates

what does a territory contain

evolution of a lower R* through delayed and lower allocation to reproduction

What characteristics will be favored by natural selection when intraspecific
competition is strong?

non-random

what distributions show territoriality?

niches must overlap

what must be true for species to have interspecific competition?

Synedra

Which will win when SiO2 is a limiting resource?

-Asterionella – R* = 1.0 or Synedra – R* = 0.4

David Tilman

studied diatoms with silica shells

Gause

Russian Ecologist, studied Parameciums

if they either depend on different resources or live at different conditions

When does Gauses principle state that species can coexist?

Joe Connel

Scottish ecologist, worked with Barnacles

rock space

what are the barnacles in Connells experiment competing for?

the S barnacles are better competitors in the low areas but have lower tolerance and cannot survive up high like C barnacles can

what is the trade off illustrated in the barnacle experiment?

C

which of the barnacle types have a greater fundamental niche?

competition affects almost every natural system and competition is only important in the absence of other natural forces

2 diffferent ecologist views on competition

niche overlap

Amount of _________ determines the degree and intensity of competition

intraspecific competition

When there is little niche overlap, what sets limits to population growth?

interspecific competition

When there is lots of niche overlap, what sets limits to population growth?

lots of niche overlap

when is competitive exclusion and character displacement possible over time?

2 resources needed by a species

What does Dave Tilman’s competition Model consider?

top right

What quadrant in Tilman’s model is good

zero net growth isocline (zngi)

line that separates our quadrants in Tilman model

fast resource usage

what does a long consumption vector mean?

combined usage of the 2 resources that can shift graph

what does the resource vector represent?

supply vector

line on graph that shows replenishment of two resources over time

average the supply and consumption vectors together

Hoe do you determine the environment shift in the 2 resource model?

populations/resources oscillate, neither species goes extinct

what happens in zone 4?

yes

Does Tilman’s model ever predict coexistance?

range of conditions and resource qualities that a species can survive under indefinitely

what is the G.Evelyn Hutchinson (current) definition of niche?