CH 54: An Introduction to Ecology and Biomes

BIO 1134

Life History

a species life history is the series of events from birth through reproduction to death.

• set of adaptions that influence survival, fertility and age at first reproduction

  • has a genetic basis and can be inherited

• natural selection favors the combination of life history traits that maximizes an individual’s output of viable, fertile offspring

Life history traits of r-selected species

• are of small size, grow rapidly, and have a short life span

• they produce many, small offspring that disperse well

• are weak competitors

• found in disturbed or unstable environments

• Ex: clownfish, wish flower

Life history traits of k-selected species

• are of large size, grow slowly, and have a long life span

• they produce few, large offspring that disperse poorly

• are strong competitors

• found in stable environments

• Ex: bears, acorns

The environment

is the selective pressure of natural selection

• consists of abiotic and biotic components

• varies in scale

  • climate

    • large spatial and temporal scale

  • microclimate

    • small spatial and temporal scale

• is influenced by both natural and anthropogenic phenomenon

Ecology

is the scientific study of the relationships and interactions between organisms and their environment

• study of how organisms interact with each other and the environment (organized into abiotic and biotic)

• provides the basis for understanding the science of environmental issue

Ecologists

follow the scientific method and conduct hypothesis-driven studies in both laboratory and field settings

• a strong understanding of statistics is important

• make verifiable observations using the discovery approach

Ecology levels

ecology can be studied at many levels

• ecologists work at levels ranging from individual organisms to the planet

• it is convenient to divide ecology into five increasingly comprehensive levels

  • organismal ecology

  • population ecology

  • community ecology

  • ecosystem ecology

  • global ecology

Organismal ecology

studies the ways that organisms adapt to environments through physiology and behavior

• Ex: what is the temperature tolerance of this zebra?

Population ecology

studies factors that influence the number and distribution of individuals in a population

• Ex: what factors influence the growth of zebra populations in Africa?

Community ecology

studies interactions between species, including predator-prey interactions, mutualism, etc.

• Ex: what factors influence the number of species in African grassland communities?

Ecosystem ecology

studies the flow of energy through ecosystems, and the cycling of matter within ecosystems

• Ex: how do water, energy, and nutrients flow among plants, zebras, and other herbivores and carnivores in African grassland communities?

Biosphere/Global ecology

studies large, global scale issues such as global climate change

Environmental science

is the interdisciplinary study of the natural and man-made world, emphasis on sociology, economics and political science

Abiotic factors of the environment

abiotic factors of an ecosystem are its nonliving components

• can have profound effect on the life within the ecosystem, geographic distribution of species, ecosystem NPP, biodiversity of an area, and number of individuals in population of species

• Factors

  • Temperature

  • Wind

  • Water

  • Light

  • Salinity

  • pH

Temperature

has a strong influence on the geographic distribution of species

• dramatic changes in habitat temperature can lead to localized extinction

• Ex: low temps freeze many plants, high temps denature proteins, some plants require fire for germination

  • coral reefs are only abundant in warm water

Water

water availability has important effects on the abundance of individuals in populations

• Ex: the relationship between the amount of rainfall and the density of buffalo, buffalo is dependent on grass availability, which itself depends on annual rainfall

• insufficient water limits plant growth and animal abundance; excess water drowns plants and other organisms

Light

can be a limiting resource for plants in both terrestrial (land) and aquatic habitats

• light, temperature, and nutrient availability all impact NPP (net primary productivity) NPP = GPP - Rs

• Ex: Algae grown at different ocean depths. Green algae at the ocean surface and absorb red and blue light, and red algae at a greater depth because their pigments absorb blue-green light that reaches such depths

• insufficient light limits plant growth, particularly in aquatic environments

pH

the pH of soil can impact the distribution and number of species in areas

• acidic, alkaline, or neutral

• Ex: species-rich flora of chalk grassland have higher pH with alkaline soil, while sparse flora is more acidic due to soil

• variations in pH affect decomposition and nutrient availability in terrestrial systems; directly influence mortality in both aquatic and terrestrial habitats

Wind

wind amplifies affects of cool temperatures (wind chill) and water loss; creates pounding waves

• Ex: animals and plants of the intertidal zone adhering to their rocky surface

Biotic factors

the living organisms of an ecosystem constitute its biotic factors

• Ex: plants, animals, predators, decomposers

Field-based control experiments

field experiments have weaker controls because nature introduces many uncontrollable factors

Laboratory-based control experiments

Lab experiments have strong, precise controls because everything can be kept constant

Organism

all living things can be called organisms, biologists classify organisms as belonging to a particular species

• Organismal ecologist - how does one organism survive?

  • how a bird migrates and navigates

Population

a group of organisms of the same species that occupy the same environment

• Population ecologist - what happens to the size and growth of the population?

  • why wolf populations decrease or increase

Community

is an assemblage of populations of different species, determined by the environment and the interactions of the species with each other

• Community ecologist - how do different species interact?

  • predator-prey interactions

Ecosystem

formed by the interactions of a community of organisms with their physical environment

• Ecosystem ecologist - how do energy and nutrients move through the whole system?

  • how sunlight affects algae growth

Biosphere

includes all of the places on Earth where living organisms exist

• Biosphere/global ecologist - how does the whole Earth work as one living system?

  • climate change and its global impact

What drives the global climate system?

the amount of solar radiation incoming (varies with latitude)

What does the incoming solar radiation establish?

the three-cell model of global circulation that determines global patterns of temperature and precipitation

• warm air rises in equatorial zone where rain is frequent year round

• above equator is secondary zone of precipitation where temperate forests are

• polar regions are cold

Regional-scale factors that influence the microclimate of a region

an areas proximity to water and topography influences its microclimate

• proximity to a major body of water (ocean currents) moderates the environment within a region

Topography

diversifies the environment within a region or locale

• rainshadows

• elevation as a substitute for latitude

Earth’s terrestrial biomes: Tundra

• long, very cold winters

• permafrost - frozen soil

• top of north pole

Earth’s terrestrial biomes: Boreal forests/taiga

(coniferous forests)

• largest terrestrial biome on Earth

• long, cold winters & short, wet summers

• coniferous trees dominate (relatively low biodiversity)

• thin acidic, nutrient poor soils

• under tundra

Earth’s terrestrial biomes: Temperate deciduous forest

• wide range of seasonal temperatures (usually 4 distinct seasons)

• deciduous trees dominate (relatively high biodiversity)

• relatively nutrient-rich soils

• under boreal forest

Earth’s terrestrial biomes: Tropical forests

• temperature - “summer” year-round

• precipitation can vary - wet or wet/dry

• habitat complexity yields high biodiversity

• nutrient poor, acidic soils

• located on the equator

Earth’s terrestrial biomes: Temperate grasslands

• treeless except along rivers and streams (fire maintained)

• hot dry summers and cold winters

• tallgrass, mixed-grass and short grass prairies

• historically deep, nutrient-rich soils

• moving from east to west across north america it is right after temperate deciduous forests

Earth’s terrestrial biomes: Chaparral

• mediterranean climate

• spiny shrubs dominate

• fire-dependent vegetation

• fragile soils prone to mudslides

• right after temperate grasslands

Earth’s terrestrial biomes: Deserts

• very hot by day, cold by night, and very dry (monsoon season)

• succulent cacti and spiny shrubs

• plants and animals greatly influence soil nutrients

• right after chaparral