Biology 11 Unit 1: Fundamentals. Lesson 1: Ecology

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1 Biology 11 Unit 1: Fundamentals Lesson 1: Ecology

2 Objectives In this section you will be learning about: ecosystem structure energy flow through an ecosystem photosynthesis and cellular respiration factors that limit population growth the process of succession

3 Ecology Biology is the study of living things and ecology is the branch of biology that is concerned with the relationships between organisms and their environments. Ecologists are concerned primarily with how organisms affect and are affected by their environment and how these interactions determine the kinds and numbers of organisms found in a particular area.

4 Ecosystems Ecologists often study individual ecosystems. An ecosystem is a community of organisms, the habitat they live in, and how they interact with one another. Ecosystems can be large (a rainforest) or small (a single tidepool or rotting log). Ecosystems are made up of biotic and abiotic components.

5 Biotic & Abiotic Components Biotic components include all of the living, or once living, things in an individual s environment (trees, birds, bugs etc.) Abiotic components are all the non-living parts or conditions in an individual s environment, such as temperature, light, water, precipitation and soil type.

6 Feeding Relationships There are many relationships within a given ecosystem. Perhaps the most obvious type of relationship is a feeding relationship. We can use food chains and food webs to represent the feeding relationships in an ecosystem.

7 Food Chains/Webs A food chain simply describes what eats what. Each step in a food chain is called a trophic level. Food chains are linked together to form complex food webs. Food webs demonstrate the inter-relationships between members of an ecosystem.

8 Food Chains The arrow in a food chain or web shows the direction of energy flow. You could replace an arrow with the words is eaten by.

9 Food Web

10 Autotrophs Autotrophs (literally meaning selffeeders ) capture the energy from sunlight or inorganic sources to make their own food. Autotrophs include plants, some algae and bacteria. They are also called producers.

11 Heterotrophs Heterotrophs must feed on other organisms for their energy. They are also called consumers.

12 Heterotrophs There are many different types of heterotrophs. Herbivores (primary consumers) eat only plants. Carnivores (secondary and tertiary consumers) eat only other animals. Omnivores eat plants and animals. Detritivores feed on plant and animal remains and other dead matter. Decomposers break down organic (biotic) matter into inorganic (abiotic) matter.

13 Trophic Levels First Trophic Level is occupied by the producers (ie. plants, phytoplankton) Second Trophic Level is occupied by the primary consumers (ie. herbivores) Third Trophic Level is occupied by secondary consumers (ie. carnivores or omnivores) Fourth Trophic Level is occupied by tertiary consumers (ie. top carnivores) Fifth Trophic Level is occupied by detritivores (scavengers) or decomposers (saprophytes)


15 Energy Pyramid Only part of the energy that is stored in one trophic level is passed on to the next level (about 10%). Organisms use much of the energy that they consume for life processes, such as respiration, movement, reproduction etc. and some of the energy is lost to the environment in the form of heat. This decline in available energy may be visually represented in an Energy Pyramid.



18 Try these links Ecology Food chains and food webs

19 Photosynthesis Remember that autotrophs, or producers, are able to produce their own food. This of course requires energy. Plant cells have organelles, called chloroplasts, that contain the pigment chlorophyll.

20 Photosynthesis Chlorophyll is able to capture light energy from the sun and use that energy to convert carbon dioxide and water into the simple sugar, glucose. This process is called photosynthesis


22 Equation The overall equation for photosynthesis is: 6 CO H 2 O + solar energy C 6 H 12 O O 2 carbon dioxide + water + solar energy glucose + oxygen

23 Cellular Respiration Since consumers cannot make their own food, they must acquire their energy by eating producers or other consumers. Consumers get the energy they need by breaking down glucose in a process called cellular respiration. This process requires oxygen and releases water and carbon dioxide. Mitochondria are responsible for cellular respiration in both plant and animal cells.


25 Equation The overall equation for cellular respiration is: 6 O 2 + C 6 H 12 O 6 6 CO H 2 O + energy oxygen + glucose carbon dioxide + water + energy You will notice that this equation is the opposite to that of photosynthesis. Thus, the circular relationship between producers and consumers forms.

26 Try this link bio104/cellresp.htm

27 Population Biology A population is a group of individuals of the same species occupying the same area. A community is made up of all of the populations of organisms found in a particular environment. Populations and communities are constantly changing.


29 Population Change The size of the population may change if new individuals are added or removed. As new populations are added to a community some may leave due to the different interactions between populations. A change in communities is called succession.

30 Succession Succession is the change in species composition over time in a given area. Primary succession occurs when organisms begin to populate an area that lacks formed soil (ie. exposed rock from a rock slide). Pioneer communities are the first species to appear during primary succession (ie. lichens and mosses).

31 Forest Succession

32 Succession Secondary succession occurs if an existing community has been cleared by some disturbance that leaves the soil intact (ie. clearcutting or a forest fire). The community passes through a series of stages to reach a relatively stable climax community. Each stage is identified by the dominant vegetative species present.

33 Lake Succession

34 Habitat A habitat is the physical area or environment where an organism lives.

35 Niche A niche refers to the organism s role in its environment. The niche of an organism includes such things as what the organism does, what its source of energy or food is, which organisms use it as a source of food, its effects on other organisms within the community and its effects on the physical environment.


37 Population Growth Populations change over time. New individuals are added to the population through reproduction (natality), others may die (mortality). The rate at which organisms are able to reproduce varies a great deal and can determine a population s potential growth rate.

38 Limiting Factors There are many factors that can contribute to mortality rate in a population, such as predation, disease, limited space, competition for resources, food shortage, water shortage, change in climate and old age. These are also known as limiting factors or environmental resistance. Almost anything affecting the lives of organisms could be considered a limiting factor.

39 igration Some individuals may leave one population to join another (emigration) and others may enter from an outside population (immigration). Do not confuse immigration and emigration with migration. In migration the entire population changes the location in which it lives and does not change in size.

40 Zebra & Wildebeest Migration in Tanzania

41 Population Density These factors (natality, mortality, emigration and immigration) change the size of the population. If there is no change in the space that the population occupies, then there is a change in population density.

42 Exponential Growth A population with no limiting factors can increase in size exponentially. An example of this kind of growth would be a population able to double in size every day (ie. bacteria). On the first day there would be one individual; on the second day, two; on the third day, four; etc with no end in sight.

43 Population Size J-Shaped (Exponential) Growth Curve If you were to plot this data on a graph we have what is known as a J-shaped growth curve. J-Growth Time

44 Carrying Capacity Limiting factors will eventually slow down the growth rate of the population until it leveled off or even decreased. Once this occurs, a population is said to have reached the carrying capacity ( the maximum number of individuals that can be supported)of its environment.

45 Logistic Growth When an organism establishes a population in a new environment, an S-curve, or logistic growth pattern is produced. The population increase is slow at first (lagphase) since there are only a few individuals able to produce new offspring.

46 Logistic Growth Then a growth- phase occurs as there are now more individuals to produce new offspring. Eventually, environmental pressures will slow the rate of increase and the growth rate levels off as it approaches the carrying capacity of the environment (plateau-phase).

47 Population Size S-Curve (Logistic) Growth Curve S-Growth Time

48 Logistic Growth If the population grows past the carrying capacity, the limiting factors of the environment will cause a death-phase and bring the population back down to the carrying capacity.

49 S-curve (showing death phase)

50 Species Interactions Intraspecies interactions involves competition between members of the same species that occupy the same ecological niche. Interspecies interactions occur between different species living together in an ecological community.


52 Species Interactions These interactions can have a positive, negative or neutral affect on a population s density. Both population density may increase (+,+), one may increase while the other decreases (+, -), one may increase while the other is not affected (+, 0), or both may decrease (-,-).

53 (+, -) Predation & Parasitism Predation involves a predator which eats its prey. Parasitism involves living on or in a host and seldom involves host death. Parasitoidism involves laying eggs on or in living hosts after hatching the larvae feed within the host s body and eventually cause death. Herbivory involves animals eating plants.

54 Predation

55 Parasite

56 Parasitoid

57 Herbivory

58 Predator-Prey Cycles Most populations fluctuate in cycles. The prey population rises, causing the predator population to also rise. Predators then overfeed on prey, causing the prey population to drop. Once the prey population drops, the predator population drops due to lack of food. The cycle repeats indefinitely.

59 Predator-Prey Cycles

60 (-, -) Competition interspecies competition occurs when two or more species in a community rely on similar limiting resources (food, shelter, space, etc.). as the population density of one species increases, it may limit the density of the competing species as well as its own The Competitive Exclusion Principle predicts that two species competing for the same limiting resources cannot coexist in the same community. One will use resources more efficiently and eventually eliminate the competition.

61 (+, 0) Commensalism Commensalism is an interaction whereby a host species is unaffected by a symbiont Example: clown fish is protected by sea anemone while sea anemone is unaffected by the presence of the clown fish


63 (+, +) Mutualism Mutualism is an interaction in which both species benefit from the relationship. Example: cleaner fish


65 Link Population Ecology

66 Assignment: You are now ready to complete your First Assignment (Quiz #1: Ecology).