BiologyCST Review PowerPoint in

Ecology

ACCORDING TO THE BLUEPRINTS…

6. Stability in an ecosystem is a balance between competing effects. As a basis for understanding this concept: a. Students know biodiversity is the sum total of different kinds of organisms and is affected by alterations of habitats. b. Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size. c. Students know how fluctuations in population size in an ecosystem are determined by the relative rates of birth, immigration, emigration, and death. d. Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration. e. Students know a vital part of an ecosystem is the stability of its producers and decomposers. f. Students know at each link in a food web some energy is stored in newly made structures but much energy is dissipated into the environment as heat. This dissipation may be represented in an energy pyramid.

Biodiversity•Biodiversity is the variation of life forms within a given ecosystem, biome, or on the entire Earth. Biodiversity is often used as a measure of the health of biological systems. The biodiversity found on Earth today consists of many millions of distinct biological species.

•Today there is concern about the mass reduction in biodiversity caused primarily by the impact humans are having on the environment, particularly the destruction of plant and animal habitats.

Question: Name some ecosystems that show

high biodiversity and low biodiversity.

Question: Why are ecosystems “healthy” if

they exhibit high biodiversity?

Question: What human practices can lead to a

reduction in biodiversity?Question: Why should a loss in biodiversity be of

great concern to us?

Introduction of Non-native Species

•An introduced, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its native distributional range, which has arrived there by human activity, either deliberate or accidental.

•Some introduced species are damaging to the ecosystem they are introduced into, others negatively affect agriculture and other human uses of natural resources, or impact on the health of animals and humans.

•The greatest impact is caused by introduced species that change an entire habitat, because many native species thrive only in a particular habitat.

•Other invaders, though they do not change a habitat, endanger single species or even entire groups of them in various ways.

Water hyacinth from South America

POPULATIONS-A population is a group of organisms of the same species that live in a particular area. -The number of organisms in a population changes over time because of the following: births, deaths, immigration, and emigration.-Births and immigration increase the size of the population; whereas, deaths and emigration decrease the size.

Emigration:Individuals leave the ecosystem.

Immigration: Individuals arrive at the habitat.

Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement.

Many factors influence population growth, for example, availability of resources, presence of

predators, diseases, etc.

Population Density

Population density may be defined as simply the number of individual organisms per unit area.

Distribution can be uniform, random, or clumped.

Uniform

Random

Clumped

Energy in the Ecosystem•The source of all food is the activity of autotrophs, mainly

photosynthesis by plants. •They are called producers because only they can manufacture food from inorganic raw materials. •This food feeds herbivores, called primary consumers. •Carnivores that feed on herbivores are called secondary consumers. •Carnivores that feed on other carnivores are tertiary (or higher) consumers. •Such a path of food consumption is called a food chain.

•Each level of consumption in a food chain is called a trophic level.

GRASS GRASSHOPPER TOAD SNAKE HAWK

Decomposers (or saprotrophs) are organisms that break down the dead or decaying organisms, and in doing so carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. Decomposers use deceased organisms and non-living organic compounds as their food source. The primary examples are bacteria and fungi.

Pyramids of Energy and Biomass

An ecological pyramid is a graphical representation designed to show the biomass at each trophic level in a given ecosystem. Biomass pyramids show the abundance or biomass of organisms at each trophic level. Ecological pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat herbivores, then carnivores that eat those carnivores, and so on). The highest level is the top of the food chain.

Loss of Matter and Energy - At each trophic level along a food chain, there is always a 'loss' of matter and energy in the forms of waste (e.g. carbon dioxide, feces), and heat and kinetic energy (e.g. constant body temperature of mammals, the energy used to move). Up to 90% of matter and energy can be 'lost' at each level.

Loss of Matter and Energy - At each trophic level along a food chain, there is always a 'loss' of matter and energy in the forms of waste (e.g. carbon

dioxide, feces), and heat and kinetic energy (e.g. constant body temperature of mammals, the energy used to move). Up to 90% of matter and energy can

be 'lost' at each level.

10% Efficiency in Energy Transfer!

Carbon Cycle

Five major reservoirs of Carbon:

a. Atmosphere

b. The terrestrial biosphere (soil, freshwater).

c. Oceans

d. The sediments including fossil fuels.

e. The earth's interior, carbon from the earth's mantle and crust

The Carbon Cycle-Plants “fix” the Carbon from CO2 into glucose through photosynthesis using light energy.-Oxygen gas is one of the products of photosynthesis.-Cell Respiration in both animals and plants break down glucose to yield energy, producing CO2 as a by-product.-O2 and CO2 cycles from plants and animals via the complementary processes of photosynthesis and respiration.

Decomposition and combustion are two other processes that

contribute CO2 gas into the atmosphere.

The Nitrogen CycleKey processes:1. Nitrogen-

fixation2. Nitrification3. Denitrification

1. Nitrogen fixation- is the process by which nitrogen (N2) in the atmosphere is converted into ammonia. This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g. nucleotides for DNA and amino acids for proteins.

1

2

3

Nitrogen Cycle, continued…

-Certain bacteria, called Nitrogen-fixing bacteria, live in nodules found in the roots of some plants. These bacteria possess the enzymes that can fix nitrogen gas into ammonia. 2. Nitrification- Nitrifying bacteria from the soil, can convert the ammonia produced by decay, into nitrates, a process called ‘nitrification.’ Plants can directly use N in the form of nitrates.3. Denitrification- Denitrification reduces nitrates to nitrogen gas, thus replenishing the atmosphere.

Legumes such as peas, clover, and beans have nitrogen-fixing bacteria

in their roots. This enables them to grow in nitrogen-poor soil. Plants take up nitrates through their roots, and convert them into proteins and

other compounds.

Ecological RelationshipsOrganisms within ecosystems may be involved in any of

these relationships…1. Symbiosis- interaction between two organisms where

at least 1 benefits. a. Commensalism- one species benefits, the other

species is not affected. b. Mutualism- both species benefit. 2. Parasitism-one species benefits, the other species is harmed. 3. Predation- one species ‘preys’ (kills for food) another species. 4. Competition- exists when species fight for food and other resources. This may be intra- or inter-specific.

This is an example of commensalism- he barnacle gains a place to live and, presumably, the scallop is not harmed.

A lamprey, is an ectoparasite.