UNIT 2:INTRODUCTION TO CLASSIFICATION►

UNIT 1: INTRODUCTION TO BIODIVERSITY

  • UNIT 1: INTRODUCTION TO BIODIVERSITY

    Key Unit Competence
    Explain how diversity is threatened by climate change and human activities
    Learning objectives
    By the end of this unit, I should be able to:
    – Define the terms: species, ecosystem and niche.
    – Explain that biodiversity is considered at three different levels
    – Evaluate the consequences of loss of biodiversity.
    – Characterize the biotic and abiotic components that define Rwanda’s
    ecosystems (example: freshwater, marine, and terrestrial).
    – Apply Simpson’s Index of Diversity.
    – Explain the importance of random sampling in determining the biodiversity
    of an area.
    – Use suitable survey methods such as frame quadrats, line and belt transects to
    assess the distribution and abundance of organisms in a local area.
    – Use Pearson’s linear correlation to analyze the relationships between the
    distribution and abundance of species and abiotic or biotic factors.
    – Recognize that the biodiversity of the earth is threatened by human activities

    and climate change

    Introductory activity: Biodiversity of Rwanda
    Read the following text and answer the questions that follow
    Rwanda is located at the heart of the Albertine Rift eco-region in the western
    arm of the Africa’s Rift Valley. Habitats of Rwanda are equally varied, ranging from
    Afro-Montana ecosystems in the northern and western regions to lowland forests,
    savannah woodlands and savannah grasslands in the southern and eastern
    regions. There are other habitats around volcanic hot springs and old lava flows,
    especially in the northern and western part of the country.

    Rwanda also has several lakes and wetlands which are rich in different species.
    Though not yet well surveyed, all these ecosystems host a rich variety of fauna and
    flora and micro-organisms. This rich biodiversity is mainly conserved in protected
    areas including three national parks, natural forests and wetlands. These cover
    almost 10 percent of the national territory while the rest of the country is densely
    populated (507 people per square kilometer in 2018).

    Many tourists visit Rwanda for its beautiful environment and biodiversity made
    of different species of plants and animals such as Aloe vera (Igikakarubamba),
    Muringa oleifera (Muringa), Phaseolus vulgaris (common bean), Nymphaea
    thermarum (Endemic plant species that cannot be met elsewhere in the world,

    only found in Mashyuza minor locality harbors), 

    Colobus polykoma (White-black colobus monkey), Gorilla gorilla (mountain
    gorilla) bird Laniarius mufumbiri (Bird species mainly found in Rweru- Mugera
    wetland),etc.

    The most attracting species in Rwanda is Gorilla gorilla whose habitat is the
    mountains of Birunga where they make a large population. Another natural forest,
    Nyugwe National Park is a terrestrial ecosystem that contains a large community
    of different plants and animals.

    Rwanda also has different lakes such as Muhazi and Rumira. They are aquatic
    ecosystems made of few species of fish, such as tilapias. Tilapias from Lake Muhazi
    are small, black and bony fish while those from Lake Rumira look red, big and soft.

    Tilapias from both lakes still belong in the same species but show variations.

    Many species of animals and plants have been discovered in Rwanda but some
    species also disappeared. Today the big garden snails known as Achatina achatina
    have become rare in Bugesera. Other people poached Rhinoceros alba living in
    Savanah of Akagera National Park.

    Honey bees, butterflies and grasshoppers are small in size but still important for
    different ecosystem services. Each organism is important for its niche in ecosystem.
    We need to identify and protect the biodiversity of our ecosystem. Many tourists
    enjoy visiting Rwanda for its biodiversity.
    1. Name the species not found elsewhere that attract the tourists and locate
    where it is found.
    2. Mashyuza is a minor locality in western province in Rusizi district that
    contributes to biodiversity of Rwanda. Give any other two locations.
    3. Define each of the following biological terms and give an example from
    the text
    abovesada) Species (b) Population (c) Community (d) Habitat (e) Ecosystem
    (f)Variation (g) Niche
    4. What causes some species to become extinct?
    5. What can be the consequences of the loss of some species from our
    biodiversity?

    6. Do you support tourism in Rwanda? Give a reason to justify your answer.

    1.1. Meaning of key ecological terms and biodiversity
    Activity 1.1
    Using addition resources to your textbook available in your school such as the
    books from the school library and search further information from the internet:
    1. Describe the following terms: biodiversity, species, niche, population, and
    community? 

    2. Differentiate between ecological niche and habitat.

    1.1.1. Key ecological terms
    Species is a group of closely related organisms which are capable of interbreeding to
    produce fertile offspring. Occasionally two organisms which are genetically closely
    related but not of the same species can interbreed to produce infertile offspring. For
    example:
    – A cross between a donkey and a horse produces a mule, which is infertile.
    Thus, a donkey and a horse do not belong to the same species
    – Lions and tigers belonging to different species. However, when a male tiger
    mates with a female lion they can have fertile offspring called tiglons, although

    the offspring of female tigers and male lions called ligers are not fertile

    Note that normally, tigers are forest dwellers and lions are plains dwellers and they
    are ecologically isolated. Breeding has only been observed in captivity.
    An ecological population is a group of individuals of the same species which live in
    a particular area at any given time.

    An ecological community consists of populations of different species which live in
    the same place at the same time, and interact with each other.

    A habitat is a specific area or place in which an individual organism lives. When a
    habitat is very small it is regarded as a microhabitat. Most ecosystems contain
    several habitats, and one species can have more than one habitat constituting its
    geographic range.

    An ecological niche is the status or the role of an organism in its habitat or the mode
    of life of an organism within its habitats. For example, insects are pollinating agents
    and preys of insectivores.

    Abiotic factor are non-living physical aspects of the environment such as the

    sunlight, soil, temperature, wind, water, and air. 

    Biotic factors are the living organisms in the environment. They include organisms
    and their interactions with each other.

    An ecosystem is a natural unit consisting of biotic and abiotic factors through
    which energy flows and nutrients recycle. In an ecosystem, nutrients pass between
    different organisms in definite pathways. For example, nutrients in the soil are taken
    up by plants, which are then eaten by herbivores, which in turn may be eaten by

    carnivores and recycled by decomposers. 

    A biome is a group of ecosystems that have the same climate and similar dominant
    communities. The highest level of organization is the entire biosphere.

    The Biosphere is the whole of the earth’s surface, the sea and the air that is inhabited
    by living organisms. The biosphere is made up of all ecosystems.

    1.1.2. Biodiversity

    Biodiversity is defined as the full range of variety and variability within and among

    living organisms and the ecological complexes in which they occur. 

    Self-assessment 1.1
    1. Describe the two main components of an ecosystem.
    2. Hippopotamus has different habitats. It was found that the resting
    habitat is different from the mating habitat, and these two habitats
    are different from the area where this animal gets food. Explain the

    ecological term given to this set of habitats.

    1.2. Identification of biodiversity
    Activity 1.2
    Use books or other sources of information to answer the followings questions:
    1. What kinds of initiatives and incentive mechanisms are put in place by
    the Government of Rwanda to motivate local community in biodiversity
    conservation?
    2. Describe different ways used to identify biodiversity.
    3. Discuss the values of biodiversity and ecosystem services in Rwanda.
    4. Evaluate the contribution of biodiversity to human well-being.
    1.2.1. Categories of biodiversity
    Biodiversity can be categorized into three groups:
    – Genetic diversity: the combination of different genes found within a
    population of a single species, and the patterns of variation found within
    different populations of the same species.
    – Species diversity: the variety and abundance of different types of organisms
    which inhabit an area.
    – Ecosystem diversity: the variety of habitats that occur within a region, or within

    the mosaic of patches found within a landscape. 

    1.2.2. Importance of biodiversity
    Biodiversity contributes to ecosystem goods and services. The ecosystem goods and
    services include:
    – Provision of food, air, fire wood, medicines(Fig.1.2), energy, fresh water.
    – Nutrient cycling such carbon, water and nitrogen cycles by microorganisms
    and primary production by photosynthesis.
    – Cultural or aesthetic service recreation, ecotourism, cultural and religious
    inspiration.

    1.2.3. The threats and consequences of biodiversity loss
    1.2.3.1. Causes of biodiversity loss
    The main causes of biodiversity loss can be attributed to the influence of human
    activities on ecosystems. Threats to biodiversity include:
    a. Habitat loss and the degradation of the environment
    The habitat loss and the degradation of the environment occur in different ways.
    The most occurring, are tree cutting, agriculture and fires (Figure1.3). These human
    activities lead to the alteration and loss of suitable habitats for biodiversity. As a
    consequence, there is a loss of plant species as well as the decrease in the animal

    species associated to this plant diversity.

    b. Introduction of invasive alien species and genetically modified organisms
    Species originating from a particular area are harmful to native species also called
    endemic species when they are introduced into new natural environments. They
    can lead to different forms of imbalance in the ecological equilibrium, so that
    endemic species may fail to compete with introduced species, and they may affect
    the abundance and distribution in natural habitat.
    c. Pollution
    Human activities such as excessive use of fertilizers, and increased pollutants from
    industries and domestic sewage affect biodiversity. They contribute to the alteration
    of the flow of energy, chemicals and physical constituents of the environment and
    hence species may die as a result of toxic accumulation.
    d. Overexploitation of natural resources
    Increased hunting, fishing, and farming in particular areas lead to the decrease and
    loss of biodiversity due to excessive and continuous harvesting without leaving
    enough time for the organisms to reproduce and stabilize in their natural habitat.
    e. Climate change
    This is a change in the pattern of weather, related changes in oceans, land surfaces
    and ice sheets due to global warming resulting from man’s activities. Increasing
    global temperatures have resulted into melting of icebergs raising sea levels and so

    flooding coastal areas eventually affecting the niche.

     1.2.3.2. Consequences of loss of biodiversity
    They are various consequences of loss of biodiversity that include:
    – Desertification, is thought by scientists to be a consequence of climate change,
    has been considered to be related to deforestation. Disrupting water cycles
    and soil structure results into less rainfall in an area.
    – Floods as a result of rising sea levels
    – Habitat destruction for extensive farming, timber harvesting and infrastructure
    and settlement
    – Decrease in food production as result of change in pattern of weather that
    affects productivity
    – Large scale deforestation has a negative effect on nutrient recycling and can
    accelerates soil erosion

    – Diseases that come as effects of floods and malnutrition due to famine

    Self-assessment 1.2
    1. Define the term Extinction.
    2. Suggest the causes of extinction of species in Rwanda.
    3. Discuss the benefits of biodiversity to humans
    4. Discuss the major factors leading to the degradation of ecosystems in
    Rwanda
    5. Discuss the contribution of ecosystems to cultural traditions in Rwanda.
    6. In Rwanda different plants are used in traditional medicine to treat different
    diseases. Conduct a research and list at least 20 medicinal plants and the
    diseases they treat. From the list above describe at least one medicinal
    plant and get ready to present your work. The project work should include:
    written content of 2 pages in minimum and 4 pages in maximum, a
    testimony of people that have used plant species.
    7. Pollution is one of the causes of aquatic biodiversity loss.
    a. What do you understand by water pollution?
    b. Outline human activities that contribute to water pollution

    c. Discuss how polluted water affects aquatic living organisms?

    1.3. Calculation of Simpson’s index
    Activity 1.3
    A survey on tree species was conducted in Gako forest by a group of students.
    Five tree species (A to E) were identified and counted. The numbers found during

    this exercise are summarized in the following table:

    1. Describe the relative abundance of species A to E.
    2. Based on the data in the above table, suggest how species diversity of tree

    species can be calculated.

    There are many ways to measure diversity. The Simpson diversity index among
    indices used to measure diversity. It is expressed in three related indices namely

    Simpson index, Simpson index of diversity and Simpson reciprocal index. 

    a. Simpson index D
    Simpson index D can be expressed in two ways and takes into consideration the
    total number of organisms of a particular species and the total number of organisms
    of all species. It is calculated as follows: D =1-∑ (n/N) 2 or D =  , with n: the total
    number of organisms of a particular species and N: the total number of organisms
    of all species. When the index equals or is nearby 0 there is an infinite diversity
    of considered species. When it equals or is nearby 1, this means that there is no
    diversity. The bigger the value of D, the lower the diversity and small is D, the bigger

    is the diversity. 

    b. Simpson index of diversity 1 – D The value of this index ranges between 0 and
    1, but now, the greater the value, the greater the sample diversity. This makes
    more sense. In this case, the index represents the probability that two individuals
    randomly selected from a sample will belong to different species.
    c. Simpson reciprocal index 1 / D
    Another way of overcoming the problem of the counter-intuitive nature of Simpson’s
    index is to take the Simpson’s reciprocal index 1 / D. The value of this index starts with
    1 as the lowest possible figure. This figure would represent a community containing
    only one species. The higher is the value of Simpson reciprocal index, the greater the
    biological diversity. 
    Examples
    1. In woodland, a quadrat was sampled for ground vegetation. Data collected were
    recorded in the table 1.3.2. Find out the value of the Simpson index and draw the
    conclusion about the biological diversity of the sampled area.

    Table 1.3.1: Recorded data on the vegetation from a woodland





    Solution: Putting the figures into the formula for Simpson’s Index:  


    Based on the meaning of Simpson index, the quadrat presents a low diversity
    because the value of D is near zero and zero and below 0.5.

    2. Calculate the value of Simpson’s Diversity Index (D) for a single quadrate sample
    of ground vegetation in woodland from which the following sampling date was

    obtained:


    Solution:



    Self-assessment 1.3

    1. Differentiate between species richness and species evenness
    2. Suggest precautions taken when measuring populations of aquatic animals
    or plants.
    3. Explain why a habitat with high diversity tends to be more stable than one
    with lower diversity.
    4. In a survey of trees in a tropical forest, students identified five tree species
    (A to E).
    They counted the numbers of trees in an area 100 m × 100 m and found
    these results:


    Calculate the Simpson’s Index diversity for identified species and explain the
    advantage of using data on species diversity and abundance when calculating an
    index of diversity.
    5. The Simpson’s Index of diversity for vegetation in an open area inhabited
    by grasslands was 0.8. For a similar sized area of vegetation beneath some

    conifer trees it was 0.2. What do you conclude from these results?

    1.4. Sampling techniques to assess the distribution and
     abundance of organisms

    Activity 1.4

    From your school garden, sample different flowering plant species and answer

    the following questions:

    1. Specify the techniques used for collecting flowers of different species.
    2. What are the advantages of the technique you used for data collection?
    3. Move around the school garden and collect different specimens of plant
    species. Name the collected species by using their names. In case you don’t
    know their names, use letters A, B, C ….
    Calculate Simpson index D, Simpson index of diversity and Simpson

    reciprocal index.

    To calculate Simpson’s index for a particular place:
    – Identify the habitat to be studied.
    – The number of individuals sampled for each species must be recorded.
    To analyze the distribution and abundance of organisms in an area of study, there
    are different sampling methods.
    Note that, sampling only one quadrat would not give reliable estimate of the

    diversity of the ground flora in the wood.

    a. Random sampling method
    A random sampling method is a sampling method where samples are taken from
    different positions within a habitat and those positions are chosen randomly.
    b. Quadrat sampling method
    A quadrat is a square area that is marked using a pre-made square of plastic, or
    stakes and string and it can range in size. Different species and their numbers within
    the quadrat are counted. Counting is repeated many times in different places in the
    habitat to get an accurate representation of biodiversity.
    c. Frame quadrats
    Frame quadrats are small plot used to isolate a standard unit of area for the study
    of the distribution of an item over a large area. While originally rectangular, modern
    quadrats can be rectangular, circular, and /or irregular. The quadrat is suitable for
    sampling plants, slow-moving animals such as millipedes and insect and some
    aquatic organisms.


    d. Transect sampling
    Transect sampling is done using a transect line, which is usually a rope or measuring
    tape that has been marked at set intervals, such as every meter. The line is unrolled
    within the habitat. At every interval, the type and number of species along the
    line are recorded. A measured line is laid across the area in the direction of the
    environmental gradient. The species touching the line can be recorded along the
    whole length of the line (continuous sampling) or at specific points along the line

    (systematic sampling).

    e. Belt transects method
    Belt transects method is the same as the line transects but widens the sampling
    area. The samples are taken and the abundance, percentage cover in a defined area

    determined. Samples can be taken within the belt. 

    f. Netting
    Netting is a sampling method where fine mesh nets are used to capture different
    organisms that include insects, birds and bats. The technique is also used for 

    sampling small aquatic organisms like daphnia, and water boatman.

    g. Capture -recapture technique
    This method is useful for sampling non-fixed population and is suitable for animal
    such as fishes, birds, lizards and insects. A sample of the population to be studied is
    first captured and each individual is marked with a spot for identification. These are
    then released and given enough time to mix up with the rest of the members in the
    habitat. After a certain period of time, another sample is taken.
    During the mark-release-recapture technique, the total population can be estimated
    by the use of the formula: , where
    n1 is a number caught and marked in first sample,
    n2 is a number caught in second sample
    n3 is a number in the second sample that had been marked.
    To understand this application, let us use the following examples:
    1. A team of students used a sweep net to sample brown grasshoppers
    and each collect insect was marked with a very small spot of non-toxic
    waterproof paint and then they were released in the field. The next day, a
    second large sample was conducted and data were recorded as follows:
    number of caught and marked in first sample (n1) = 247, number of caught
    in second sample (n2) = 269, and the number in the second sample that had

    been marked (n3) = 16. What is the number of estimated population?

    Solution
    The estimated number = = 4152 grasshoppers
    2. A student collected 16 butterflies which he marked and released. For a second
    time he collected 18 butterflies among which 12 were already marked from the

    first sampling. Estimate the population size of butterflies in that area.

    Solution

    The estimated number 24 butterflies

    Self-assessment 1.4
    1. Explain the advantages of the random sampling techniques.
    2. Use suitable methods, such as frame quadrats, line transects, and belt
    transects, to assess the distribution and abundance of insect species in a
    school garden. Record your data and use the Simpson index of diversity (D)
    to calculate the diversity of collected insects.
    3. Suggest the benefits of using the following sampling techniques:
    a. Quadrats
    b. Transect
    c. Mark-capture-recapture
    4. State the conditions in which quadrats, transect and mark recapture are

    suitable sampling methods.

    1.5. Pearson’s linear correlation
    Activity 1.5

    Some of the following figures indicate a positive, negative or non-correlation.

    1. What do you understand by the term correlation?
    2. Categorize the graphs given as positive, negative or weak or no correlation
    3. In which conditions results can indicate a positive correlation?
    4. Conclude about your results when there is no correlation.

    To decide if there is an association between collected data, a correlation coefficient
    is calculated and plot scatter graph drawn in order to make a judgment. The
    strongest correlation is present for studied items when all the points lie on a straight

    line. In this case, there is linear correlation, and the correlation coefficient equals

    1. If a given variable X increases so does another variable Y, the relationship is a
    positive correlation. If a variable X increases while the variable Y decreases, then
    the relationship is a negative correlation. A correlation coefficient of 0 means there
    is no correlation at all. These correlation coefficients are ways to test a relationship
    observed and recorded to see if the variables are correlated and, if so, to find the

    strength of that correlation.

    a. Pearson’s correlation coefficient
    Pearson’s correlation coefficient can only be used where there might be a linear
    correlation and when there are collected quantitative data as measurements (for
    example, length, height, depth, and light intensity, mass) or counts (for example
    number of plant species in quadrats). The data must be normally distributed. 

    Where:
    r is the correlation coefficient
    x is the number of species in a quadrat
    y is the number of species in the same quadrat
    n is the number of readings (From1 to n)
    x is the mean number of species
    y is the mean number of species
    sx
     is the standard deviation for x
    s
    y

     is the standard deviation for y

    Self-assessment 1.5

    Use Pearson’s linear correlation to analyze the relationships between the

    distribution and abundance of species and abiotic or biotic factors.

    End of unit assessment 1
    Section A: Answer as true or false
    1. Abiotic factors are the non-living physical aspects of the environment.
    2. Capture –recapture is a method used to integrate the numbers of mobile
    animals in a particular place.
    3. A correlation coefficient of 0 means that there is no correlation at all.
    4. A sample is a portion, piece, or segment that is representative of a whole
    area of study.
    5. In the Simpson’s index, N represents the total number of organisms of a
    particular species
    Section B: Long and short answer based questions
    1. What do you understand by the term biodiversity?
    2. What do you think would happen to plants if there were no insects?
    3. Suggest different ways to conserve our forests.
    4. A student has randomly collected 5 types of species at the following

    frequencies.

    Calculate the Simpson’s diversity index of this community.
    5. A team of students conducted the capture- recapture sampling method
    of tilapia from lake Muhazi at different times of the day as recorded in the

    data below:

    a. Plot the graph for the date provided and describe the shape of the
    graph.
    b. From the graph, determine the appropriate time to have the most
    catch.
    6. What do you understand by term endangered species?
    7. Describe how diversity is threatened by climate change and human

    activities

    UNIT 2:INTRODUCTION TO CLASSIFICATION►