Topic 4.1 – Species, Communities, Ecosystems Understandings  Species are groups of organisms that can potentially interbreed to produce fertile offspring.  Members of a species may be reproductively isolated in separate populations.  Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).  Consumers are heterotrophs that feed on living organisms by ingestion.  Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.  Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.  A community is formed by populations of different species living together and interacting with each other.  A community forms an ecosystem by its interactions with the abiotic environment.  Autotrophs obtain inorganic nutrients from the abiotic environment.  The supply of inorganic nutrients is maintained by nutrient cycling.  Ecosystems have the potential to be sustainable over long periods of time

Topic 4.1 – Species, Communities, Ecosystems Skills and Applications  Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.  Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)  Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.  Skill: Recognizing and interpreting statistical significance.

What is a SPECIES?  Group of organisms that can potentially interbreed and produce fertile offspring  Similar physiological and morphological characteristics  Can produce fertile offspring (hybrids are not fertile!)  Genetically distinct from other offspring  Have a common phylogeny (family tree)  The interbreeding and interacting members of a species is called a POPULATION  Members of species may be reproductively isolated in separate populations

What are COMMUNITIES?  An ecological community consists of all the interacting populations in an area  The populations in a community interact in the following ways: predation, parasitism, competition

What are ECOSYSTEMS?  of all of the communities within a defined area, along with the ABIOTIC (nonliving) environment  study of ecosystems focuses on the flow of energy and nutrients  pathways of energy and nutrients to understand the factors shape interactions within communities, and between communities and the nonliving environment

Topic 4.2 – Energy Flow Understandings  Most ecosystems rely on a supply of energy from sunlight.  Light energy is converted to chemical energy in carbon compounds by photosynthesis.  Chemical energy in carbon compounds flows through food chains by means of feeding.  Energy released from carbon compounds by respiration is used in living organisms and converted to heat.  Living organisms cannot convert heat to other forms of energy.  Heat is lost from ecosystems.  Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

Topic 4.2 – Energy Flow Skills and Applications  Skill: Quantitative representations of energy flow using pyramids of energy.

How do Energy and Nutrients move through ecosystems?  Nutrients are atoms and molecules that organisms obtain from their living or nonliving environment and that are required for survival  constantly cycle and recycle within and among ecosystems  change in form and distribution  Energy moves in a one-way flow through communities within ecosystems  continuously replenished  used and transformed in the chemical reactions that power life  ultimately converted to heat that radiates back into space

Energy Flow Through Ecosystems  Energy enters ecosystems mainly through photosynthesis  energy stored in the chemical bonds of sugar molecules  produce food using nonliving nutrients and sunlight  Autotrophs: have the ability to make their own organic molecules  PHOTOSYNTHESIS – uses light energy and inorganic molecules to produce organic molecules  CHEMOSYNTHESIS – uses inorganic molecules such as hydrogen sulfide to produce organic molecules (instead of sunlight) Sugar is synthesized and used in plant tissues plant tissues, growth Energy is captured from sunlight Carbon dioxide is absorbed from the air Oxygen is released Water is absorbed from soil, used in photosynthesis, and stored in cells Inorganic mineral nutrients (nitrate, phosphate) are absorbed from soil and used in plant tissues photosynthesis

O2O2 CO 2 H2OH2O sugar plant tissues other nutrients energy from sunlight photosynthesis Photosynthesis Fig. 28-1

Energy Flow Through Ecosystems  Energy passes from one trophic level to another.  producers (autotrophs)  first trophic level  primary consumers (herbivores)  second trophic level  feed on producers  Secondary consumers (carnivores & omnivores)  Tertiary consumers  third and fourth trophic levels  meat-eating predators  Decomposers  Everything dies and nutrients must be brought back into cycle  Detritivores, Saprotrophs

Energy Flow Through Ecosystems TERTIARY CONSUMER (4th trophic level) PRODUCER (1st trophic level) A simple terrestrial food chain (a) SECONDARY CONSUMER (3rd trophic level) PRIMARY CONSUMER (2nd trophic level)

Energy Flow Through Ecosystems SECONDARY CONSUMER (3rd trophic level) A simple marine food chain (b) Phytoplankton PRODUCER (1st trophic level) Zooplankton PRIMARY CONSUMER (2nd trophic level) TERTIARY CONSUMER (4th trophic level)

Energy from sunlight detritus feeders and decomposers primary consumers producers HEAT higher-level consumers HEAT NUTRIENTS heat energy solar energy energy stored in chemical bonds nutrients HEAT

solar energy heat nutrients heat energy energy stored in chemical bonds detritus feeders and decomposers primary consumers higher-level consumers producers energy from sunlight nutrients O S P N Mg H Ca H2OH2O

Can you identify the different trophic levels?

Energy Flow Through Ecosystems  An ecosystem’s contribution to Earth’s productivity depends upon both the ecosystem’s net primary productivity per unit area and its prevalence. desert (90) open ocean (125) continental shelf (360) tundra (140) coniferous forest (800) temperate deciduous forest (1,200) grassland (600) tropical rain forest (2,200) estuary (1,500)

Energy Pyramid for a Grassland Fig. 28-6

biological magnification  Because of the inefficiency of energy transfer, certain persistent toxic chemicals become increasingly concentrated in the bodies of animals that occupy increasingly higher trophic levels by a process called  Mercury taken up by producers can be highly concentrated in carnivores such as swordfish, and are a health hazard to humans as a result