Community Interactions Introduction Levels of Organization • Ecologists study organisms and their environments at different levels of organization: – Biosphere: consists of all organisms on Earth – Biome: group of ecosystems that have the same climate and dominant communities. – Ecosystem: consists of living things and their environment. – Community: consists of populations of different species that live in the same area and interact together. – Population: organisms of the same species that live in the same area, interact with one another, and produce fertile offspring. – Organisms: are individual living things. This is the lowest level of organization that ecologists study. Biologists study organisms, organ systems, organs, tissues, cells, organelles, and molecules. Chemists study atoms and subatomic particles. Organisms and the Environment • Organisms: life form consisting of one or more cells; has characteristics of life. • Environment includes both living (biotic) and nonliving things (abiotic). Biotic and Abiotic Factors • Biotic living organisms • Abiotic nonliving or physical factors • Together determine productivity of the ecosystem in which organisms’ live Community Interactions • Powerfully affect an ecosystem • Include: – Competition – Predation – Symbiosis Competition • When organisms of the same or different species attempt to use an ecological resource at the same place and the same time – Resource any necessity to life – Plants and animals compete – Winner and losers • Interspecific competition – Competition between same two species – When 2 or more species rely on same limited resource in a community – Ex. African savannah Rules, rules, rules • Fundamental rule in ecology – Competitive Exclusion Principle • Russian biologist G.F. Gause – Paramecium caudatum vs. Paramecium aurelia • 2 species so similar in requirements that the same resource limits both population’s growth, and one species may succeed over another • No two species can occupy the same niche in the same habitat and the same time • Prevents competition Niche • Each species unique living arrangement in a community • “Role” • Ex. Lizards in a rainforest • Includes: – Habitat – Food sources – Time of day organism is most active Predation • Interaction where an organism captures and feeds on another organism • Predator – Organism that does the killing and eating • Prey – Organism that is being killed and eaten (victim) Predator Adaptations • • • • Speed Agility Coloring/camouflage to ambush prey Packs/teams – Ex. Wolves • Acute senses – Ex. Rattle snake heat sensor organs • Claws, teeth, fangs, stingers, poison Prey adaptations • • • • Safe locations Flee Coloring/camouflage to hide Defensive coloration – “warning coloration” • Mimicry – Organisms imitate dangerous organisms by appearance and actions • Hawk moth larva • Plants – Thorns, spines, poisonous chemicals Symbiosis • Any relationship where two species live closely together • Symbiosis literally means “living together” • 3 main types – Parasitism – Mutualism – commensalism What type of relationship is this? • Who is helping who? Mutualism • Both species benefit from the relationship • A Happy couple • Flowers and bees – Flowers need bees for pollination, bees need flowers nectar What type of relation ship is going on here? • Who is helping who? Commensalism • One member of the relationship benefits while the other is neither harmed nor helped • One-sided • Food or shelter • Barnacles on whale Ants and aphids What type of interaction is going on here? Parasitism • One organism lives on or inside another organism and harms it • Parasite obtains all or part of its nutrients from the other organism • Host – Organism that is harmed in relation ship; the one that provides the nutrients to the parasite • Parasite – Organism that gets its nutrients from the host • Do they want to kill their host? – No, because they need them…they will weaken or hurt the host in some way What Is a Population? In biology, a population is a group of organisms of the same species that live in the same area. How large a population is and how fast it is growing are often used as measures of its health. Population Growth Rate • Population growth rate (r) is how fast a population changes in size over time. A positive growth rate means a population is increasing. A negative growth rate means it is decreasing. The two main factors affecting population growth are the birth rate (b) and death rate (d). Births and Deaths: Balancing Costs of Reproduction and Survival • growth rate = birth rate – death rate r=b–d Other Factors Affecting Population Growth Rate Population growth may also be affected by people coming into the population from somewhere else (immigration, i) or leaving the population for another area (emigration, e). The formula for population growth takes all these factors into account. • r = (b + i) - (d + e) r = population growth rate; b = birth rate; i = immigration rate; d = death rate; and e = emigration rate Patterns of Population Growth • At first, exponentially then logistically until carrying capacity is reached After 5 hours of exponential growth; one bacteria yields… 32,768 Limits to Population Growth • limiting factor is a property of a population’s environment – living or nonliving – which controls the process of population growth. Biologists have identified two major types of limiting factors: – Density-dependent factors – Density-independent factors. What Is a Community? Communities are made up of populations of different species. A community is the biotic part of an ecosystem. It consists of all the populations of all the species in the same area. It also includes their interactions. What Is an Ecosystem? An ecosystem is a unit of nature and the focus of study in ecology. It consists of all the biotic and abiotic factors in an area and their interactions. Ecosystems can vary in size. A lake could be considered an ecosystem. So could a dead log on a forest floor. Both the lake and log contain a variety of species that interact with each other and with abiotic factors. Ecosystem Components • Niches • Habitats • Competitive Exclusion Principle The Niche Niche organism’s occupation (role), where it lives, and way in which organism’s use conditions they exist in – Food it eats – Place in food web – How it gets food – Range of temperatures needed for survival – When and how it reproduces The Habitat • Physical environment to which an organisms has become adapted and survives in. Competitive Exclusion Principle • Two different species cannot occupy the same niche in the same geographic area. If they do they will compete with one another for the same food and other resources. Eventually, one species will out compete the other. What Are Biomes? A biome is a group of similar ecosystems with the same general abiotic factors and primary producers. Biomes may be terrestrial or aquatic. Terrestrial Biomes Terrestrial biomes include all the land areas on Earth where organisms live. The distinguishing features of terrestrial biomes are determined mainly by climate (abiotic factor). Terrestrial biomes include tundras, temperate forests and grasslands, chaparral, temperate and tropical deserts, and tropical forests and grasslands. Terrestrial Biomes and Climate • Climate is the average weather in an area over a long period of time. Weather refers to the conditions of the atmosphere from day to day. • In terms of moisture, climates can be classified as arid (dry), semi-arid, humid (wet), or semihumid. The amount of moisture depends on both precipitation and evaporation. • Biomes are categorized based upon their climate types. Climate and Biodiversity Climate determines plant growth, it also influences the number and variety of other organisms in a terrestrial biome. Biodiversity generally increases from the poles to the equator. It is also usually greater in more humid climates. Climate and Adaptations Organisms evolve adaptations that help them survive in the climate of the biome where they live. For example, in biomes with arid climates, plants may have special tissues for storing water. The desert animals also have adaptations for a dry climate. In biomes with cold climates, plants may adapt by becoming dormant during the coldest part of the year. Dormancy is a state in which a plant slows down cellular activities and may shed its leaves. Animals also adapt to cold temperatures. One way is with insulation in the form of fur and fat. Survey of Terrestrial Biomes Terrestrial biomes are classified by climatic factors and types of primary producers. Aquatic Biomes Terrestrial organisms are generally limited by temperature and moisture. Therefore, terrestrial biomes are defined in terms of these abiotic factors. Most aquatic organisms do not have to deal with extremes of temperature or moisture. Instead, their main limiting factors are the availability of sunlight and the concentration of dissolved oxygen and nutrients in the water. Aquatic Biomes and Sunlight In large bodies of standing water, including the ocean and lakes, the water can be divided into zones based on the amount of sunlight it receives: 1. The photic zone extends to a maximum depth of 200 meters; enough sunlight penetrates for algae and other photosynthetic organisms to photosynthesize. 2. The aphotic zone is water deeper than 200 meters; too little sunlight penetrates for photosynthesis to occur. As a result, food must be made by chemosynthesis or else drift down from the water above. Aquatic Organisms Aquatic organisms generally fall into three broad groups: plankton, nekton, and benthos. They vary in how they move and where they live. 1. Plankton are tiny aquatic organisms that cannot move on their own. They live in the photic zone. They include phytoplankton and zooplankton. Phytoplankton are bacteria and algae that use sunlight to make food. Zooplankton are tiny animals that feed on phytoplankton. 2. Nekton are aquatic animals that can move on their own by ‘‘swimming” through the water. They may live in the photic or aphotic zone. They feed on plankton or other nekton. Examples of nekton include fish and shrimp. 3. Benthos are aquatic organisms that crawl in sediments at the bottom of a body of water. Many are decomposers. Benthos include sponges, clams, and anglerfish which are adapted to a life in the dark. What Is the Biosphere? The biosphere is the global sum of all ecosystems; integrating all living beings and their relationships, including their interactions with the elements of the lithosphere, hydrosphere, and atmosphere. QUICK REVIEW •What is community? •What is population? Recap • What are the three types of interactions in a community? – Competition – Predation – Symbiosis • What types do we have? – Mutualism – Commensalism – Parasitism Ecological Succession • Do all ecosystems stay the same all the time? • What are some things that cause changes to ecosystems? – Natural and unnatural – Quickly and slowly • Ecosystems are constantly changing in response to human and natural disturbances. • As an ecosystem changes, older habitants die out and new organisms move in, causing more change Ecological Succession • Series of predictable changes that occur in a community over time – Physical environment – Natural disturbance – Human disturbance Primary Succession • Succession on land that occurs on surfaces where no soil exists • Volcanic eruptions • Glaciers melting Stages of Primary Succession • Start with no soil, just ash and rock • First species to populate this area – “pioneer species” – For example, pioneer species on volcanic rock are lichens (LY-kunz) • Lichens made up of fungus and algae that can grow on bare rock • When lichens die, they for organic material that becomes soil…now plants can grow Secondary Succession • Succession following a disturbance that destroys a community without destroying the soil • Natural – hurricane – fires • Human disturbances – Farming – Forest clearing Succession in Marine Ecosystems • Deep and dark • Can succession happen? • 1987 dead whale off of California – Unique community of organisms living in remains – Represents stage in succession in an otherwise stable, deep-sea ecosystem – Whale-fall community Whale-Fall Succession • Begins when large whale dies – Sinks to barren ocean floor – Scavengers and decomposers flock to carcass , our first community • Amphipods • Hagfish • sharks • After a year, most tissues have been eaten – Now, second small community of organisms live here – Body is decomposing, releasing nutrients into the water • • • • Small fishes Crabs Snails worms • Only skeleton remains… – Third community moves in • Heterotrophic bacteria • Decompose oil in bones release of chemical compounds • Who uses these chemical compounds? – Chemoosynthetic autotrophs • In come the crabs, clams, and worms that feed on this bacteria Human Activity and Species Diversity • Land clearing – Farmland – Diverse forest replaced with single crop – Decreases species diversity • Introduced species – Humans move a species from its native land to a new location, intentionally or accidentally Study Chapter 35, Population Ecology and Community Interactions Teacher,
