Lecture Twenty Three - Biosphere I Flashcards
Define ecology.
The scientific study of the interaction between organisms and their environment.
What is the scope of ecology?
Interaction between organisms and their environments - distribution and abundance.
Ecology and evolutionary biology closely related.
Ecological research ranges from the adaptations of individual organisms to biosphere dynamics.
Ecology = a scientific context for evaluating environmental issues.
Explain ecology and the biosphere.
Ecology - the scientific study of the interactions of organisms and their environment.
Biosphere:
- The region of the Earth where life exists.
- The ‘global ecosystem’ = the sum of all the planets ecosystems.
Biosphere - extends from the depths of the oceans to about 6000 m above sea level.
Most organisms live within a few meters of the earths surface.
Many live deep beneath the ocean.
Few live at high altitudes - highest is a high altitude adapted moss.
Abiotic factors controlling the biosphere: Temperature. Water. Sunlight. Wind. Rocks and solid. Disturbance. All of these contribute to the climate.
What are the major components of the biosphere?
Atmosphere - think envelope of air around the Earth.
Hydrosphere - Earths water, occurs as liquid water (surface and underground), ice (polar ice, icebergs and permafrost) and water vapour.
Lithosphere - Earth’s crust and upper mantle.
–> Crust contains non-renewable fossil fuels, minerals and renewable soil chemicals.
The biosphere includes most of the hydrosphere, and parts of the lower atmosphere and upper lithosphere.
What are the abiotic facts which affect the distribution of organisms?
Temperature - some organisms can only tolerate specific ranges of temperature.
Water - some organisms can only tolerate either fresh or salt water.
Sunlight - provides energy that drives nearly all ecosystems.
–> The intensity and qua lit of light and photoperiod are important to the development and behaviour of many organisms.
How is an organisms distribution and abundance determined?
Distribution and abundance of an organism is determined by their interactions between organisms and their environments.
How are ecology and evolutionary biology closely related?
Includes investigating how organisms respond to the environment and how organisms are distributed.
Events that occur in the framework of ecological time (minutes, months, years) translate into effects over the longer scale of evolutionary time (decade, centuries, millennia and longer).
Ecology provides a scientific contact for evaluating environmental issues.
What are the facts which affect the distribution of organisms?
Species dispersal.
Behaviour and habitat selection.
Biotic factors.
Abiotic factors.
What is biogeography?
The study of past and present distributions of individual species - a starting point for understanding the things that limit geographic distributions.
Ecologists ask questions to determine what factors limit the geographical distribution of a species.
What is a microclimate?
Climate varies on a small scale - microclimate e.g. forest floor, under rocks.
Cleared areas - greater temperature extremes than forest interiors, due to greater solar radiation and wind currents.
Ecotones exist between communities, and gradients within them.
What is primary production of ecosystems?
The total amount of light converted to chemical energy by photosynthesis.
Requires sold and water to support energy capture and flow - ecosystem dynamics.
Global primary production on land is crucial component of biochemical cycles.
E.g. carbon cycle.
Explain coral reefs and productivity.
Coral reefs such as the great barrier reed are ‘islands’ of high production in an open sea of very low primary productivity.
Some reefs (atlantic) characterised by low diversity and low abundance of phytoplanktivores.
Annual primary productivity 1500-3500gcm^2.
Explain aquatic biomes.
Aquatic bimes occupy the largest part of the biosphere.
Marine biomes have a salt concentration of ~3% and cover approximately 75% of the Earths surface.
Freshwater biomes - salt concentration of < 1% –> Closely linked to the solids and biotic components of the terrestrial biomes through which they pass.
The speed of water flow and the climate are also important.
Fresh water biomes:
Littoral zone is shallow and close to the shore.
Limnetic zone is the opera surface water.
Profundal zones consists of the deep aphasic regions.
Lakes:
Oligotrophic lakes are deep, nutrient poor - do not contain much life.
Mesotrophic lakes have moderate amounts of nutrients and phytoplankton productivity.
Over long periods of time, oligotrophic lakes may become mesotrophic as runoff brings in nutrients.
Pollution from fertilisers -> explosion in algae population -> decrease in oxygen content.
Eutrophic lakes are shallower, have increase nutrients.
Explain terrestrial biomes.
Defined by their abiotic and biotic factors.
Vertical stratification is also important.
- Tropical rain forest canopy - the top layer, covering layers below.
- Permafrost in the tundra (a permanently frozen stratum).
Species composition of any biome differs from location to location.
Human activity - radically altered natural patterns of many biomes.
Tropical forests:
Close to the equator, very high amounts of rainfall (although this varies from region to region), and very high biodiversity.
Vegetation layered - the canopy being one of the top layers.
Fertile soils.
Little leaching of minerals - enclosed ecosystem.
Savannas:
Grasslands with scattered trees, that show distinct seasons, particularly wet and dry.
- Support many types of plants and animals.
- Fire an important abiotic facts = frequent, low intensity.
Soils are highly fertile and often black from high C content.
Deep soils where roots penetrate.
High productivity - above ground productivity dies off, reruns N, P C to soil.
Deserts:
Very low rainfall, generally hot.
Vegetation usually sparse - cacti and succulents, grasses and acacias.
Many nocturnal animals - adaptations to thermoregualte.
Chaparral:
Essentially ‘heathlands’ - mild wet winters, hot dry summers.
Comprise dense spiny, evergreen shrubs, subject to frequent fires.
Some plants produce seeds that will only germinate after fire.
Temperate grass lands:
Seasonal drought, frequent summer fires.
Extensive alienation and exploitation for grazing and a agriculture.
Temperature deciduous forests:
Support dense stands of trees and have very cold winters and hot summers.
Trees lose leaves - winter dormant.
Large variety of plant sand animals.
Coniferous (boreal) forests:
Larges terrestrial biome of Earth.
Exhibit long cold winters and short wet summers.
Conifers adapted.
Inhabited by various animals, some of whig hibernate.
Cold, low productivity, acidic litter (fulvic acid), little human accumulation, leached of minerals.
Tundra:
Characterised by low-growing plants.
Climate windy, cold - short growing season.
Permafrost found <1 meter and does not thaw, prevents root growth therefore not many animals.
Two types, arctic (areas of Alaska and the Arctic circle) and alpine, found on very high mountains.
