Ecosystems: Interactions, Energy and Dynamics

Ecosystem An open system (including the community of living things and their non-living environment) through which energy flows

Energy flows throughout an ecosystem Energy is transferred between organisms (chemical energy) – Organic matter (food) At each step, some energy is lost as heat

Input into Ecosystem Solar radiation is the main input into all ecosystems Captured by photosynthetic organisms

Input into an Ecosystem Atmosphere filters most wavelengths of the EMS Optical “window” can get through the atmosphere (UV  visible  IR)

UV radiation UVA ( nm) – Ozone layer cannot absorb – Ages skin UVB ( nm) – Ozone layer can partially absorb – Damages DNA (forms DNA crosslinks), can result in cell death or mutations – Causes sunburns – Ages skin – Stimulates vitamin D production UVC ( nm) – Ozone layer completely absorbs

Activity: UV-sensitive yeast Yeast with a mutation in enzyme in UV damage repair pathway

Results from Increased UV exposure Increased susceptibility to disease, death – Disrupt development of very young organisms (eggs, larva) – Dangerous during reproductive age (pass mutations on to future generations) Impairs photosynthesis and/or changes flowering time of some plants Disrupts organisms to different extent – Shift species composition of ecosystems

Causes of Increased UV exposure Depletion of the ozone layer – Hole in ozone layer in the Antactic  decreased phytoplankton in surface water. Huge impact on ocean food chains, carbon cycle (ocean carbon storage) Loss of shade or protection from UV light – Loss of shade trees/ thick forests – Water bodies (shallower or clearer water cannot filter as much UV)

Input into an Ecosystem

Absorbed vs Reflected Sunlight Sunlight contains a range of visible light wavelengths – What color is sunlight? If an object reflects a certain wavelength of visible light, it will look that color to your eye What if an object absorbs all visible wavelengths of light? What if an object reflects all visible wavelengths of light?

Activity: Calculating the Energy Flowing Through an Ecosystem 1.Measure the amount of incident (incoming) solar radiation.

Photosynthetic organisms Chlorophyll: family of pigments that absorb energy from specific wavelengths of light

Photosynthesis Photo: conversion of light energy into chemical energy (ATP) – Energy from light feeds into an electron transport chain (in membranes of chloroplasts) Synthesis: assembly of organic compounds – Carbon fixation: fixing carbon into organic molecules

Photosynthesis 2012 Pearson Education, Inc.

Energy traveling through the Ecosystem Solar radiation enters the ecosystem Photosynthetic organisms convert light into chemical energy (organic matter)

Activity: Calculating the Energy Flowing Through an Ecosystem 2.Complete an Ecosystem Energy Budget

Pyramid of Energy At each step, energy available to the organism in the next level drops off.

Pyramid of Energy

Activity: Food Chains and Webs Producers: Autotrophs – Organisms that can synthesize their own organic matter from inorganic sources (CO 2 ) – Photoautotrophs Use light as an energy source Photosynthetic plants, algae Consumers: Heterotrophs – Organisms that require a supply of organic matter from their environment – Chemoheterotrophs Use organic (or inorganic) compounds as an energy source – Wide range of animals Herbivores, carnivores, omnivores – Primary consumers, secondary consumers, tertiary consumers, etc

Food Chains and Webs Decomposers: Saprophytes Consume dead/decaying matter, convert it to inorganic substances Important for recycling key nutrients through the ecosystem Bacteria, fungi

Food Chains and Webs

Searching for Food Sources (Foraging) Need to locate appropriate food sources, which may be difficult. Foraging Strategies – Specialist foragers (only one type of food source) (ex) Giant panda – Generalist foragers (multiple types of food sources) (ex) human, raccoon

All food sources are not equal Size of food source Nutritional value Abundance of the food source Energy used/inherent risk in obtaining the food

Activity: Foraging

Ecological Succession Gradual changes in an ecosystem where populations succeed each other Usually plant-driven or plant-dominated, animal populations change in response

Ecological Succession Primary Succession – Colonization of bare ground Sand dunes, volcano flows, mud flats, glacial till Secondary Succession – Replacement of a community after a disturbance Disturbance may be natural or caused by humans Abandoned fields, areas after a fire

Stages of Succession Recognizable stages, may be overlap or skip a stage, each can last variable time period 1.Pioneer stage – First colonizers Terrestrial: pioneer plants Aquatic: plankton 2.Seral stages (may be more than one) – Each point in continuum has characteristic community of species 3.Climax stage – Mature, self-sustaining stage

Ecological Succession

Primary vs Secondary Succession Primary Succession

Example: Primary Succession on Mt. Hood in Oregon ology/notes/succ/primary.htm ology/notes/succ/primary.htm