SPECIES, COMMUNITIES & ECOSYSTEMS The continued survival of living organisms including humans depends on sustainable communities. Topic 4.1 IB Biology Miss Werba

SPECIES, COMMUNITIES & ECOSYSTEMS TOPIC 4 – ECOLOGY 4.1 SPECIES, COMMUNITIES & ECOSYSTEMS 4.2 ENERGY FLOW 4.3 CARBON CYCLING 4.4 CLIMATE CHANGE

THINGS TO COVER U.1 U.2 U.3 U.4 U.5 U.6 U.7 U.8 Statement Guidance Species are groups of organisms that can potentially interbreed to produce fertile offspring. U.2 Members of a species may be reproductively isolated in separate populations. U.3 Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods). U.4 Consumers are heterotrophs that feed on living organisms by ingestion. U.5 Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion. U.6 Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion. U.7 A community is formed by populations of different species living together and interacting with each other. U.8 A community forms an ecosystem by its interactions with the abiotic environment.

THINGS TO COVER U.9 U.10 U.11 S.1 S.2 Statement Guidance Autotrophs obtain inorganic nutrients from the abiotic environment. U.10 The supply of inorganic nutrients is maintained by nutrient cycling. U.11 Ecosystems have the potential to be sustainable over long periods of time. S.1 Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition. S.2 Setting up sealed mesocosms to try to establish sustainability. (Practical 5) Mesocosms can be set up in open tanks, but sealed glass vessels are preferable because entry and exit of matter can be prevented but light can enter and heat can leave. Aquatic systems are likely to be more successful than terrestrial ones.

THINGS TO COVER S.3 S.4 Statement Guidance NOS 3.1 Testing for association between two species using the chi-squared test with data obtained by quadrat sampling. To obtain data for the chi-squared test, an ecosystem should be chosen in which one or more factors affecting the distribution of the chosen species varies. Sampling should be based on random numbers. In each quadrat the presence or absence of the chosen species should be recorded. S.4 Recognizing and interpreting statistical significance. NOS 3.1 Looking for patterns, trends and discrepancies —plants and algae are mostly autotrophic but some are not.

ECOLOGICAL DEFINITIONS U.1 Ecology: The study of the relationships between living organisms and between organisms and the environment Species: A group of organisms that can potentially interbreed to produce fertile offspring.

ECOLOGICAL DEFINITIONS U.2 Habitat: The environment in which a species normally lives or the location of a living organism Population: A group of organisms of the same species who live in the same area at the same time Members of a species may be reproductively isolated in separate populations.

ECOLOGICAL DEFINITIONS U.7 U.8 Community: A group of populations of different species living together and interacting with each other. Ecosystem: A community (biotic) interacting with its abiotic environment Temp Light Water Humidity pH Nutrients Wind Tides Turbidity

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CLASSIFYING ORGANISMS U.3 S.1 Species can be classified according to their method of nutrition: Autotrophs Heterotrophs However, a few species have both methods (NOS 3.1).

CLASSIFYING ORGANISMS U.3 S.1 Autotroph: An organism that synthesises its organic molecules from inorganic substances Photosynthesis Heterotroph: An organism that obtains its organic molecules from other organisms Digestion

Looking for patterns, trends and discrepancies. AUTOTROPH EXCEPTIONS NOS 3.1 Looking for patterns, trends and discrepancies. Plants and algae are mostly autotrophic but some are not.

AUTOTROPH EXCEPTIONS Sundews Sacoglossan sea slugs NOS 3.1 Sundews are carnivorous plants autotrophic but they "hunt" for insects to get additional nutrients, eg. nitrogen  Sacoglossan sea slugs are heterotrophic perform kleptoplasty to capture intact, functional chloroplasts from algal food sources and retain them within specialised cells in their digestive system 

CLASSIFYING ORGANISMS Producers: Do not consume! Mostly autotrophs Covert light energy into chemical energy Produce their own organic matter

CLASSIFYING ORGANISMS U.4 S.1 Consumers: that feed on living organisms by ingestion ingests other organic matter that is living or recently killed Classified by what they eat: can be herbivores, omnivores or carnivores Also classified according to their level in the food chain: can be primary, secondary or tertiary consumers

5.5.2 DIET MISS J WERBA - TERM 4 2010 16

5.5.2 DIET MISS J WERBA - TERM 4 2010 17

5.5.2 MISS J WERBA - TERM 4 2010 18

CLASSIFYING ORGANISMS U.5 U.6 S.1 Decomposers: organisms that decompose organic material eg. bacteria and fungi Detritivores heterotrophs that obtain organic nutrients from detritus by internal digestion Saprotrophs heterotrophs that obtain organic nutrients from dead organisms by external digestion

SOURCE OF NUTRIENTS U.9 U.10 Autotrophs obtain inorganic nutrients from the abiotic environment. The supply of inorganic nutrients is maintained by nutrient cycling. Decomposers (saprotrophic bacteria and fungi) recycle nutrients by returning them to the soil for plants to use.

SOURCE OF NUTRIENTS U.9 U.10 C H2O N

SUSTAINABLE ECOSYSTEMS Ecosystems have the potential to be sustainable over long periods of time. Set practical 5 – Setting up sealed mesocosms to try to establish sustainability. Click to read the related article

SUSTAINABLE ECOSYSTEMS Mesocosms are: Small scale investigations Self-sustaining natural systems Allow a bridge between controlled lab experiments and more variable, uncontrolled field investigations. Allow more variables to be controlled Allow sufficient complexity to model the natural environment

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 An important question to answer in any population size experiment is how can we decide if our data fits any of the known/expected ratios. A statistical test that can test out ratios is the Chi-Square Chi-Square Formula: Degrees of freedom (df) = n-1 where n is the number of groups investigated

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Let’s do an example with a dihybrid genetic cross. The expected ratio for a Mendelian dihybrid cross between heterozygotes is 9:3:3:1 The following data was obtained for 556 seeds: Observed Values 315 Round, Yellow Seed 108 Round, Green Seed 101 Wrinkled, Yellow Seed   32 Wrinkled, Green 556 Total Seeds

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Let’s do an example with a dihybrid genetic cross. Firstly, the expected values need to be determined: Observed Values Expected Values 315 Round, Yellow Seeds (9/16) x 556 = 312.75 Round, Yellow Seeds 108 Round, Green Seeds (3/16) x 556 = 104.25 Round, Green Seeds 101 Wrinkled, Yellow Seeds (3/16) x 556 = 104.25 Wrinkled, Yellow Seeds   32 Wrinkled, Green Seeds (1/16) x 556 =   34.75 Wrinkled, Green Seeds 556 Total Seeds

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Let’s do an example with a dihybrid genetic cross. Then, apply the formula: 𝜒 2 = 0.47 Then, calculate the degrees of freedom: df = n – 1 = 4 groups – 1 = 3

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Let’s do an example with a dihybrid genetic cross. Then, we need to use the Chi-Square table at df = 3. We need to see if the probability of our chi-square value is greater than the value in the table. By statistical convention, we use the 0.05 probability level as our critical value.

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Let’s do an example with a dihybrid genetic cross. If the calculated chi-square value is less than the 0.05 value, we accept the hypothesis – ie. That the results match the expected ratios. If the value is greater than the value in the table, we reject the hypothesis – ie. That the results do not match the expected ratios. Therefore, because the calculated chi-square value of 0.47 is less than the critical value of 7.81, then we accept the hypothesis that the data fits a 9:3:3:1 ratio.

CHI SQUARE ( )TESTS 𝝌 𝟐 We are going to do this in a “prac” :) We are going to do a quadrat survey of an “ecosystem” to try to determine the number of organisms in the community. This will involve counting the number of organisms in randomly selected sample areas and trying to generalise them to the population.

CHI SQUARE ( )TESTS S.3 S.4 𝝌 𝟐 Some of you will be establishing our sampling area. Some of you will counting and randomly distributing the organisms into our sampling area. Some of you will be randomly selecting the quadrats and counting the organisms within. Then we will use the known area to estimate the population sizes. Then we will use a chi square test to check the accuracy of our estimate!

SPECIES, COMMUNITIES & ECOSYSTEMS Q1. Zoophobas morio is an insect. Its larvae feed on bat faeces in caves in Guatemala. What type of organism is a Zoophobas morio larva? Autotroph Consumer Detritivore Saprotroph J WERBA – IB BIOLOGY 32

SPECIES, COMMUNITIES & ECOSYSTEMS Q2. Which of the following ecological units includes abiotic factors? A community An ecosystem A population A trophic level J WERBA – IB BIOLOGY 33

SPECIES, COMMUNITIES & ECOSYSTEMS Q3. Define the term random sample. The masses of two different populations of sparrows (Passer domesticus) are shown in the table below. Calculate the mean value of the mass of birds for population 1. With reference to the data shown, explain what is meant by the term standard deviation. No calculation is expected. Population 1:
 mass of birds / g Population 2:
 mass of birds / g 24.5 25.0 24.0 24.8 26.9 23.2 23.6 31.0 27.9 28.3 J WERBA – IB BIOLOGY 34

SPECIES, COMMUNITIES & ECOSYSTEMS Q4. In communities, groups of populations live together and interact with each other. Outline the importance of plants to populations of other organisms in a community. 6 marks J WERBA – IB BIOLOGY 35