Living Things! Factors that affect living things are: Biotic factors – things that are alive or were alive (other organisms) Abiotic factors – things that are non-living (temperature, water etc.) The interaction of all biotic and abiotic factors creates an ecosystem.

Ecology The branch of biology that studies the way living things interact with each other and with their physical environment. It looks at the ways an organism is affected by its surroundings and how the environment is affected by the presence and activities of the organisms.

Biotic or Abiotic?

Roles of Organisms All living things need energy to survive and grow. The source of this energy is the sun. Plants through photosynthesis (an endothermic process) create food (sugar), to store energy for later use. To release stored energy from the sugar the plants carry out respiration ( an exothermic process). Not all organisms can produce their own food, so some must depend on other organisms as a source of food (energy). Organisms can be either producers, consumers or decomposers (detritivores) in terms of energy flow through an ecosystem.

Producers: are self feeding organisms (autotrophs) that make organic molecules (glucose) during the process of photosynthesis. Photosynthesis uses energy from the sun plus the inorganic molecules CO2 and H2O. Examples: Algae, grasses, trees, etc.

Consumers: are heterotrophs, organisms that cannot make their own food, they depend on other living organisms for food. Primary Consumers: Herbivores that each vegetation Ex. : Grasshoppers, rabbits, snails, etc. Secondary Consumers: Carnivores that eat the herbivores Ex. : cats, ladybugs, foxes, owls, etc. Tertiary Consumers: Top carnivores. Ex. : Lions, bears, wolves, etc.

The Decomposers (Detritivores) : They decompose dead organic material or wastes to return essential nutrients to the soil. These nutrients help plants grow. Ex. : Bacteria and mushrooms

Trophic (feeding) level refers to the organisms position in the food chain Autotrophs are at the base (first trophic level). Organisms that eat autotrophs are called herbivores or primary consumers (second trophic level). An organism that eats herbivores is a carnivore and a secondary consumer. (third trophic level) A carnivore that eats a carnivore that eats a herbivore is a tertiary consumer (forth trophic level). Omnivores eat both animals and plants.

Example of a food chain and the associated trophic (feeding) levels Organisms Grasses Grasshopper Ladybug Raven Mushrooms Bacteria Type Producer (plants) Primary Consumer (herbivore) Secondary Consumer (carnivores) Teriary Consumer (top carnivore) Decomposer Trophic Levels First Second Third Fourth Feed off all levels

An overview of Trophic and Consumer levels Organism Classification Consumer level Trophic level Food source Plants ------------------ First Herbivores primary Second plants Carnivores secondary or higher (top) Third animals Omnivores all levels plants & animals Detritivores --------------- ---------------- detritus

Food Chains and Webs

Food Chains

Energy and Nutrient Flow Through the Ecosystem The movement of energy is shown by the dark arrows. The movement of the inorganic nutrients is shown by the open arrows

grass  grasshopper  mouse  snake  hawk Food Chains and Webs A food chain is the path of food from a given final consumer back to a producer. (The arrow points to the consumer.) grass  grasshopper  mouse  snake  hawk Identify the autotrophs and heterotrophs, and classify each as a herbivore, carnivore, etc.

Feeding Levels

Food Webs Identify the autotrophs and heterotrophs, and classify each as a herbivore, carnivore

The real world is more complicated than a simple food chain The real world is more complicated than a simple food chain. A more realistic depiction of who eats whom is called a food web which depicts interlocking food chains.

Questions to answer From the previous slide identify: 1. Producers 2. Primary consumers 3. Secondary consumers 4. Tertiary consumers 5. Top carnivores

ENERGY At each level of the food chain, about 90% of the energy consumed is lost in the form of heat. The total energy passed from one level to the next is only about one-tenth of the energy received from the previous level organism. As you move up the food chain, there is less energy available to pass on to the next level. As you move up the food chain animals get larger and need more food to meet their energy needs. NOTE!! Each organism in the food chain is only transferring one-tenth of its energy consumption to the next organism.

To summarize The ultimate source of energy (for most ecosystems) is the sun. The ultimate fate of energy in ecosystems is for it to be lost as heat. Energy and nutrients are passed from organism to organism through the food chain as one organism eats another. Decomposers remove the last energy from the remains of organisms and release nutrients back into the soil. Inorganic nutrients are cycled, energy is not.

Ecological Pyramids

Ecological Pyramids: represent graphically the structure of an ecosystem Pyramid of Energy Flow : shows the energy that flows through each trophic level; notice that there is less energy at each higher level.

Pyramid of Numbers: shows the actual size of populations.

Pyramid of Biomass: measures the biomass ( g/m² ) of the organisms in a food chain (dry mass).

Toxic Substances in Food Chains!

Feeding the human population is big business (effort and monetary) To prevent crops from being eaten by insects, agriculture has turned to various chemicals that kill the insects or that interfere with their life-cycle (reproduction) In small doses, these chemicals are not harmful to other organisms, however, when they enter the food chains and move to high trophic levels, the quantities accumulate and can cause harm.

Bioamplification (Bio-magnification): Accumulation of toxins in a food chain so that the major effects are found in the food predators. Example: DDT: a pesticide used in the 50s and 60s to control populations of body lice, fleas and mosquitoes). Later used as a crop pesticide, after which sign of trouble appeared!!!!!

DDT- Belugas- St. Lawrence River

World’s Biomes

All the Earth’s ecosystems make up what is called the ecosphere or biosphere Climate is the main factor that determines whether a given species will thrive in an area. Biologists have divided the terrestrial (land) portion of the biosphere into biomes (collection of ecosystems that are similar) Biomes are large regions with a distinct climate and specific life forms Each biome is made up of many ecosystems with communities adapted to varieties in soil, climate and other factors throughout the biome.

Biodiversity: the genetic diversity, species diversity and ecological diversity that are important to life on this planet. It is the results of adaptations in organisms that have developed over billions of years in response to: *the variety of environments found on earth *competition amongst organisms for resources

Populations

A Population Group of organisms of the same species living in the same place at the same time Individuals may come and go, but the population can remain the same Ex: The flamingos of Lake Victoria in Africa. Assembled for yearly migration.

In a food web, each organism survives by gaining energy from the trophic level below it. The size of the populations then, are continually adjusted by the species interactions with both its food supply and it’s predators.

Carrying capacity: the largest population of a species that an environment can support. 4 main factors that determine the carrying capacity: 1. materials and energy: energy, water, carbon, and other essential nutrients 2. food chains: the population size is limited by the size of the populations at lower trophic levels. (Prey limited by their predators and their food supply). 3. competition: each organism has the same need as any other. They compete for resources such as food, water, mates, space. 4. density: depending on their size, environment and way of life, different species have different needs for space.

Closer look at competition: Two types of competition: 1. intraspecific: among members of the same species 2. interspecific: between different species

A closer look at population density: Two types of factors can also limit population sizes. 1. density-dependent factors: these are factors that increase as the population gets bigger and eventually lead to a decrease in the population size by increasing death rate and lowering birth rate. * overcrowding *parasites/disease *aggression amongst members * neglect of offspring

2. density-independent factors: can limit a population regardless of its original size. * forest fire * flood * volcano * weather: El Nino

Population Growth Since all organisms reproduce, populations tend to grow over time If unlimited resources are present, growth will be exponential It will proceed very quickly for rapidly reproducing organisms and more slowly for slowly reproducing ones The curve, however, will always be a “J” curve or an exponential growth curve

Generation # of bacteria time 1 1 0 2 2 15min 3 4 30min 4 8 45min 5 16 1hr 6 32 75min 7 64 90min 8 128 105min 9 256 2hrs 10 512 11 1024 12 2048 13 4096 3hrs 14 8192 15 16,384 16 32,768 17 65,536 4hrs 18 131,072 19 262,144 20 524,288 21 1,048,576 5hrs 22 2,097,152 23 4,194,304 24 8,388,608 25 16,777,216 6hrs

Population Growth 2 Gypsy moth caterpillar Resources are never unlimited, though. As population rises, resources decline. If the growth is too rapid, resources are rapidly depleted and a population crash can occur This pattern occurs often with many populations (including humans) For example... Gypsy moth caterpillar

Reindeer

Population Growth 3 More often what happens is that the resources slowly decrease, the growth rate slowly increases, and they meet. This point that they oscillate around is the carrying capacity of the environment for that particular organism S - shaped curve

Human Growth Patterns What are the causes of the rapid growth of human populations? What are some possible consequences of this growth pattern? What will our future look like? (Remember the Reindeer?)