Environmental Science - Lecture 7

What are the basics of evolution?

cumulative genetic changes that occur in a population of organisms over time

• current Theorist: Charles Darwin

What did Charles Darwin propose?

natural selection: individuals with more favorable genetic traits are more likely to survive and reproduce

• frequency of favorable traits increase in subsequent generations (Adaptation)

What are four natural conditions leading to natural selection?

High Reproductive Capacity

Heritable variation

Limits on Population Growth

Differential Reproductive Success

What is High Reproductive Capacity?

organisms tend to produce more offspring than will survive to maturity

What is heritable variation?

individuals vary in traits that may impact survival (including mutation)

What is limits on population growth?

struggle for existence

• outside pressure on which individuals all survive

What is differential reproductive success?

best adapted individuals reproduce more successfully than less adapted individuals

What is the modern synthesis of early ideas on evolution?

ecologists synthesized Darwin’s theory with growing knowledge of genetics, molecular biology, developmental biology and fossil record

Explains with mutations (changes in DNA)

• genetic variability

• changes that can be beneficial, harmful or little impact

• selected for or against

What are prokaryotes?

do not possess a cell nucleus or any other membrane bound organelles

What are eukaryotes?

possess a high degree of internal organization (nuclei, mitochondria, chloroplasts)

What are archaea?

frequently live in oxygen-deficient environments: often adpated to harsh conditions

What is bacteria?

all other prokaryotes; thousands of species; important in biogeochemical cycles

What are some principles of population ecology?

Population: group of individuals of same species living in the same geographic area at the same time

Population ecology: study of populations; how and why numbers change over time

What is population ecology important for?

endangered species

invasive species

proper management

What does population density measure?

number of individuals per unit area or volume at a given time

What are changes in global population driven by?

relative magnitudes of birth and death rates

r = b - d

r = growth rate

b =- births (births/1000 people)

d = deaths (deaths/1000 people)

For changes in local population, movement must also be taken into account.

r = (b+d) - (i-e)

r = growth rate

b = births / 1000 people

d = deaths/ 1000 people

i = immigration / 1000 people

e = emmigration / 1000 people

What is the maximum population growth under hypothetical ideal conditions?

intrinsic rate of growth ( biotic potential )

• larger organisms, smaller rates

• smaller organisms, faster reproduction, larger intrinsic rates of increase

Per each species, what history characteristics show a specific growth rate?

age of onset of reproduction

fraction of lifespan for reproductions

number of reproductive periods

number of offspring per reproductive period

What is an environmental limit?

resistance to intrinsic growth where it prevents indefinite reproduction and unfavorable food, water, shelter, predation

resistance that increase with higher populations functions → negative feedback mechanism

What is a carrying capacity?

maximum number of individuals an environment can support

causes leveling off of exponential growth

Under slow changes can lead to an S-shaped curve of ____

logistic population growth

What is overshooting carrying capacity?

can lead to a population crash and abrupt decline in density

What are factors that affect population size?

density dependent factors

density independent factors

What are density dependent factors?

factor whose effect on population changes as population density changes

• predation, disease, competition

• BOOM or BUST population cyclces

What are density independent factors?

factors that affects population size, but it is not influence by changes in population density

• killing frost, severe blizzard, fire

What is survivorship?

probability a given individual will survive to be a particular age

• Type I: death rates greatest at old age

• Type II: Death rates consistent throughout lifespan

• Type III: Death rates greatest among the young

What are biological communities?

an association of different population of organisms that live and interact in same place at same time

What is an ecological niche?

organisms role within the community

all organisms aspects are taken into existence:

• physical, chemical, biological factors needed to survive

• habitat

• abiotic components of the environment

consumption or production of resources for other’s organisms

What is fundamental niche?

potential idealized ecological niche

What is the realized niche?

actual niche the organisms occupies

What are limiting resources?

any environmental resource that, because it is scarce or at unfavorable levels, restricts the ecological niche of an organism

(nutrient, food, territory, water)

What is competition?

interaction among organisms that vie for the same resource in an ecosystem

• Intra-specific: comp between individuals in population

• Inter-specific: competition between individuals in 2 different species

• alter effective availability of resources, changing population curves over time

What is competitive exclusion?

our species excludes another from a portion of the same niche as a result of competition for resources

What is resource partitioning?

coexisting species’ niche differ from each other

What is symbiosis?

close relationship between members of two or more species (benefit/harm/unaffected)

Three types of symbiosis?

Mutualism

Commensalism

Parasitism

What is Mutualism?

symbiotic relationship in which both members benefit

What is commensalism?

symbiotic relationship where one species benefits and the other is neither harmed nor helped

What is parasitism?

symbiotic relationship in which one species is benefited and the other is harmed

What are species richness?

number of different species in a community

• varies by location

• tropical rainforests = high species richness; isolated island = low species richness

a balance of two provides overall stability in numbers as they shift in relative abundance