Introduction to Ecological Systems (HL IB Environmental Systems & Societies (ESS))

Introduction to Ecological Systems

The biosphere

• The biosphere refers to the narrow, life-supporting zone around the Earth

  • It is where the air (atmosphere), water (hydrosphere) and land (lithosphere) meet

• The biosphere contains all living organisms, including:

  • Plants (flora)

  • Animals (fauna)

  • Fungi and microorganisms

• It can be thought as one large, complex system of living communities, as well as their interactions with each other and with the non-living components of the Earth's systems, all interacting as a single unit

The biosphere measures approximately 20 km from top to bottom—however, most life exists in a narrow range of 6.5 km (500 m below sea level and 6 km above sea level)

Species

• A species is a group of organisms sharing common characteristics that interbreed to produce fertile offspring

  • This is known as the biological species concept

  • Members of the same species share a gene pool, meaning that they can breed and produce offspring with similar traits

Populations

• A population is a group of organisms of the same species living in the same area at the same time which interbreed

  • A population can be seen as an interbreeding unit of a species

• One species may consist of any number of populations, from one to many—for example:

  • The Eastern Grey Kangaroo is a species of marsupial native to Australia

  • This species consists of multiple populations across various regions of Australia

  • There are populations of Eastern Grey Kangaroos in Queensland, New South Wales, Victoria and other parts of the country

  • Although individuals from these different populations are capable of interbreeding, in reality they very rarely do due to the fact that they are geographically isolated (separated) from each other

  • Each population may have its own unique characteristics and adaptations based on local factors such as habitat, climate and food availability

  • Despite being part of the same species, these populations may exhibit some small genetic and behavioural differences due to their isolation and local environmental conditions

Community

• A community includes all of the different populations (of different species) living in the same area at the same time

  • A community is a collection of interacting populations within an ecosystem

  • For example, each species within a community depends on other species for food, shelter, pollination, seed dispersal, etc.

Habitat

• A habitat is the local environment in which an organism, species, population or community normally lives

  • E.g. badgers, deer, oak trees and ants are all species that would live in a woodland habitat

  • A description of the habitat of a species can include both geographical and physical locations, as well as the type of ecosystem required to meet all environmental conditions needed for the survival of the organism, species, population or community

Ecosystems

• An ecosystem refers to a community of living organisms, along with their physical environment, interacting as a system within a specific area

  • This includes the living, biotic components (such as plants, animals, fungi and microorganisms) interacting with the non-living, abiotic components (such as soil, water, air, sunlight, temperature, humidity and minerals)

  • These abiotic components provide the essential resources and conditions necessary for the survival and functioning of the biotic community

  • Together, the interactions between biotic and abiotic components shape the structure and dynamics of the ecosystem, influencing factors such as biodiversity, nutrient cycling and ecosystem services

• Ecosystems vary in size, from small ponds to vast forests

• Each ecosystem has its own unique characteristics, shaped by factors like geography, climate and the species present within it

• Ecosystems are open systems in which both energy and matter can enter and exit. For example:

  • Photosynthetic organisms such as plants and algae capture sunlight, which is the primary source of energy for ecosystems

  • Energy exits ecosystems primarily through heat released during cellular respiration, lost during trophic transfers (e.g. from herbivores to carnivores) and radiated from the Earth's surface into space

  • Matter can enter or exit ecosystems in the form of water, nutrients, gases or waste products produced by animals