bio 2 - ch 34 ecology (post)

ecology

study of interactions of organisms with each other and with their physical environment

• multiple levels of study

  • basic level

  • population level

  • community level

• not just descriptive but also predictive -? analyzes levels of organization and develops models and hypotheses that can be tested

basic level of ecology studies

study how organisms are adapted to their environment → why a fish species in a coral reef lives only within a certain temperature range

population level of ecology studies

study factors that affect the growth and regulation of population size

community level of ecology studies

study how various extrinsic factors (weather) and intrinsic factors (species competition for resources) affect the size of the population

population

all the organisms belonging to the same species within an area at the same time

• part of a species

species

all of the populations of similar organisms that are capable of interbreeding and producing viable offspring

community

all of the various populations at a particular locale

• a coral reef xxx contains many populations of fish species, crustaceans, and corals

ecosystem

encompasses a community of populations as well as non living environment

• ie energy flow and chemical cycling in a coral reef can affect the success of the organisms that inhabit it

biosphere

the portion of the entire Earth’s surface - air, water, land - where living organisms exist. knowing the composition and diversity of an ecosystem is important to the dynamics of this level

goals of ecology

• develop models that explain and predict patterns of distribution and the potential abundance of organisms

• consider distribution and abundance of populations across the biosphere

applications of ecology

• Managing plants and wildlife

• Identifying and use of renewable and nonrenewable resources

• Preservation of habitats and natural cycles

• Maintaining food resources

• The ability to predict the impact and course of diseases, such as malaria or coronaviruses

rate of natural increase ( r )

the growth rate that a population size can change by

• ie if a population has 1000 members and the birth rate is 30/year and death rate is 10/year the growth rate is

• (30-10)/1000 = .02 = 2%

• related to the biotic potential

*does not include immigration or emigration

biotic potential

a population's maximum capacity to reproduce and survive under ideal environmental conditions.limiting factors include:

• Number of offspring per reproductive event that survive until they are old enough to reproduce

• Amount of competition within a population

• Age distribution of the members of the population - especially the number of reproductive females present

• Presence of disease and predators

exponential growth

J-shaped curve where the more of a species the more growth expected

• often unsustainable due to the environment

• includes: lag phase and exponential growth phase

environmental resistance

all environmental conditions that prevent populations from reaching their biotic potential:

• limited food supply

• accumulation of waste products

• increased competition

• predation

increases as population grows larger

lag phase of exponential growth or logistic growth

growth is slow because the population is small

exponential growth phase of exponential growth or logistic growth

growth is accelerating and the population is exhibiting its biotic potential

logistic growth

when population growth levels off resulting in a S-shaped pattern

• includes; lag phase, exponential growth phase, logistic growth phase, and stable equilibrium phase

logistic growth phase - logistic growth

the rate of population growth slows down

stable equilibrium phase - logistic growth

little if any growth takes place because births and deaths are equal

• occurs at the carrying capacity of the environment

carrying capacity

• is the number of individuals of a species that a particular environment can support

• related to stable equilibrium phase of logistic growth

practical implications of logistic growth

the model predicts that exponential growth occurs only when population size is much lower than the carrying capacity

• when limiting growth of a pest we should reduce the carrying capacity

  • simple reducing the population size only encourages exponential growth to begin again so that is not helpful. we have to make the environment unideal

what do population growth curves assume?

all individuals are identically aged but in reality individuals are in different life stages

cohort

members of an original group of individuals born at the same time that are still alive after certain intervals of time

• plotting the number surviving over time gives the survivorship curve

  • 3 types

type I curve of survivorship

characteristics of a population in which most individuals survive well past the midpoint and death comes near the end of the maximum life span (ie humans)

type II curve of survivorship

survivorship decreases at a constant rate throughout the life span (ie songbirds)

type III curve of survivorship

typical for a population to have most members die young (ie oysters)

• since death comes early for most members only a few live long enough to reproduce

what is the shape of the curve of human population growth?

J shape

doubling time of human population growth

growth rate being described with the length of time it takes for the population size to double - considered to be 40 years for humans

zero population growth

occurs when the birthrate equals the death rate; this can be achieved only if the per capita rate of increase declines

how to decrease the expected growth in LDCs

• establish/strengthen family planning programs

• use social progress to reduce desire for large families

• delay onset of childbearing

age-structure diagram

divides the population into three groups: prereproductive, reproductive, and postreproductive

• The LDC’s have more females entering reproductive years than older women leaving them

replacement reproduction

each person replaced by one child. Misconception that zero population growth occurs if couples have only two children

• This does not cause zero population growth as long as there are more females entering their reproductive years than older females leaving them (as is common in LDC’s)

MCD

• typified by countries in NA and Europe

• low population growth/high standards of living

• doubled their populations between 1850 and 1950

LCD

• typified by countries in LA, Africa, and Asia

• expanding population growth/low standard of living

age structure for MDC’s

•it is more typical that the number of people in the prereproductive class roughly equals the number in the reproductive age class.

•This results in a stable age structure, in which population numbers are expected to remain the same

age structure for LDC’s

They have more females entering reproductive years than older women leaving them

• An unstable age structure characterizes a population that will expand rapidly

life history patterns

They are patterns are characterized by how long it takes to reach reproductive maturity and the level of reproductive output.

1. Opportunistic pattern (r-strategist)

2. Equilibrium pattern (K-strategist)

opportunistic pattern

populations that are small in size, mature early, and have a short life span

• also called r-strategist species which have many small offspring and forego parental care in favor for a greater number of offspring

  • the more offspring the more likely it is some will survive to a reproductive age

    • ie weeds and insects

equilibrium pattern

a population that remains at carrying capacity and allocates energy to growth and survival and that of their offspring follows this pattern

• also called k-species which tend to be large, slow to mature, and have long life spans

  • species that are also vulnerable to extinction when normal way of life is altered

    • ie birds and mammals

  • specialists rather than generalists

abiotic factors

include factors such as weather and natural disaster are density independent factors that influence all populations the same regardless of size

• tend me be seen in opportunistic life history patterns

relationship between prey and predator population

if the prey population declines then bad things will happen to the predators population

biotic factors

factors such as competition, predation, and parasitism which are all density-dependent factors. the effects of them depend on the size of the population - the denser the population the faster a disease may spread

• tend me be seen in equilibrium life history patterns

competition

occurs when members of two different species try to utilize the same limited resource

• density-dependent factor

ecological niche

is the role a species plays in the community, including the habitat it requires and its interactions with other organisms

• essentially a species total way of life and thus includes the resources needed to meet its energy, nutrients, survival, and reproductive demands

• competition exclusion principle

competitive exclusion principle

• No two species can occupy the same ecological niche at the same time if resources are limited

• One species will out-compete the other

resource partitioning

• Division of feeding niches

• Decreases competition between two species and allows occupancy of different niches and therefore survival

competition between two lab populations of paramecia

When grown alone, Paramecium aurelia and Paramecium caudatum exhibit logistic growth

When the two species are grown together in mixed culture, P. aurelia outcompetes P. caudatum, which dies out

competition between two lab populations of barnacles

Balanus barnacles outcompete Chthamalus barnacles at lower depthsin

Chthamalusis more resistant to drying and can survive in the upper intertidal zone

intraspecific competition

competition within a species, is often the greatest

• Nearly identical requirements for survival produces competition when resources are limited

predation

occurs when one organism, the predator, feeds on another, the prey

• types of predators

  • Animals such as lions that kill zebras

  • Animals such as filter-feeding whales that strain krill from ocean waters

  • Deer that feed on a farmer’s corn

cycling of populations

Predator and prey populations tend to cycle instead of maintaining a steady state

Cycling can occur when:

• Predators overkill prey, causing the predator population to decline in number

• The prey overshoots the carrying capacity and suffers a crash, causing the predator population to crash due to lack of food

  • In either case, the result would be a series of peaks and valleys in population density of both species

antipredator defenses

•In plants, sharp spines of cactus; pointed leaves of holly; and tough, leathery leaves of oak trees all discourage predation by insects

•In animals, poisonous secretions, concealment, fright, flocking together, warning coloration, and mimicry are methods to discourage predation

coevolution

when two species adapt in response to selective pressures imposed by the other, is seen in antipredator defenses

mimicry

occurs when one species resembles another species that has evolved to defend against predators, or when a species resembles an object in the environment to help them capture food or avoid being preyed upon

• batesian and mullerian

batesian mimicry

a prey that is not harmful mimics another species that has a successful antipredator defense

• Warning colorations are often involved

• a flower fly and a longhorn beetle are incapable of stinging another animal, and yet they have the same appearance as the yellow jacket wasp

mullerian mimicry

species that resemble each other share the same successful defenses

• A bumblebee and a yellow jacket wasp are Müllerian mimics because they have a similar appearance and both use stinging as a defense

symbiosis

refers to close and long-term interactions between members of different species

• parasitism, commensalism, and mutualism

• level of benefit or harm between species depend on what is being measured

parasitism - symbiosis

• A parasite derives nourishment from another organism called the host

• The parasite benefits, and the host is harmed

• Parasites also get a place to live and/or reproduce

• they exist in each kingdom

  • disease causing bacteria (strep infections)

  • protists (malaria)

  • fungi (athletes foot)

  • plants (mistletoe)

  • animals (tapeworm)

commensalism - symbiosis

• One species benefits; the other is neither benefited nor harmed

• One species provides a home and/or transportation for the other

  • Clownfish and sea anemones (venomous tentacles offer protection)

  • Cattle egrets and cows

mutualism - symbiosis

• both organisms benefit but degree may not be equal

  • Insects that feed on pollen gain a meal, while the plants increase their reproductive chances

  • The bullhorn acacia tree is adapted to provide a home for a species of ants, especially by providing a place for larvae to grow and develop

    • The tree benefits because the ants provide protection against caterpillars

cleaning symbiosis - mutualism

• Vertebrates serve as hosts to be cleaned by another species

• includes crustacean, fish, and birds that are cleaners

• larger fish are cleaned by smaller fish

• cleaning may provide fitness for large fish by ridding them of parasites

ecological succession

is a change in a community’s composition that is directional and follows a continuous pattern of extinction and colonization by new species

• primary succession

• secondary succession

primary succession (land)

establishment of a plant community in a newly formed area lacking soil formation

secondary succession

the return of a community to its natural vegetation following a disturbance

• Pioneer species: first species to begin the process of secondary succession

models of succession

• used to explain succession and predict future events

• climax-pattern model

• facilitation model

• inhibition model

• tolerance model

tolerance model of succession

predicts that different plant types can colonize at the same time.

• Random chance determines which arrives first

inhibition model of succession

says that colonizing species hold on to space until they die or are damaged

facilitation model of succession

suggests that each successive community prepares the environment for the next

• Grasses are necessary before shrubs, and then shrubs before trees—sequential process

climax-pattern model of succession

suggests that particular areas will always lead to a specific climax community - exact composition does not need to be the same