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Biodiversity in Ecosystems

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Title: Biodiversity in Ecosystems


1
Biodiversity in Ecosystems
  • IB syllabus 3.1
  • AP syllabus
  • Ch 5,

2
3.1 An introduction to biodiversity
  • Biodiversity is a broad concept encompassing the
    total diversity of living systems, which includes
    the diversity of species, habitat diversity and
    genetic diversity.
  • Species diversity in communities is a product of
    two variables the number of species (richness)
    and their relative proportions (evenness).
  • Communities can be described and compared through
    the use of diversity indices. When comparing
    communities that are similar, low diversity could
    be indicative of pollution, eutrophication or
    recent colonization of a site. The number of
    species present in an area is often indicative of
    general patterns of biodiversity.

3
  • Habitat diversity refers to the range of
    different habitats in an ecosystem or biome.
  • Genetic diversity refers to the range of genetic
    material present in a population of a species.
  • Quantification of biodiversity is important to
    conservation efforts so that areas of high
    biodiversity may be identified, explored, and
    appropriate conservation put in place where
    possible.
  • The ability to assess changes to biodiversity in
    a given community over time is important in
    assessing the impact of human activity in the
    community.

4
3.2 Origins of Biodiversity
  • Biodiversity arises from evolutionary processes.
  • Biological variation arises randomly and can
    either be beneficial to, damaging to, or have no
    impact on, the survival of the individual.
  • Natural selection occurs through the following
    mechanism.
  • 1. Within a population of one species, there is
    genetic diversity, which is called variation.
  • 2. Due to natural variation, some individuals
    will be fitter than others.
  • 3. Fitter individuals have an advantage and will
    reproduce more successfully than individuals who
    are less fit.
  • 4. The offspring of fitter individuals may
    inherit the genes that give that
  • advantage.
  • This natural selection will contribute to the
    evolution of biodiversity

5
  • Environmental change gives new challenges to
    species those that are suited will survive, and
    those that are not suited will not survive.
  • Speciation is the formation of new species when
    populations of a species become isolated and
    evolve differently from other populations.
  • Isolation of populations can be caused by
    environmental changes forming barriers such as
    mountain formation, changes in rivers, sea level
    change, climatic change or plate movements. The
    surface of the Earth is divided into crustal,
    tectonic plates that have moved throughout
    geological time. This has led to the creation of
    both land bridges and physical barriers with
    evolutionary consequences.
  • The distribution of continents has also caused
    climatic variations and variation in food supply,
    both contributing to evolution.
  • Mass extinctions of the past have been caused by
    various factors, such as tectonic plate
    movements, super-volcanic eruption, climatic
    changes (including drought and ice ages), and
    meteorite impactall of which resulted in new
    directions in evolution and therefore increased
    biodiversity.

6
vocabulary
  • Biodiversity
  • Diversity
  • Diversity index
  • Genetic Diversity
  • Habitat diversity
  • Isolation
  • Plate Tectonics
  • Species Diversity
  • Speciation
  • Species

7
Diversity
  • A generic term for heterogeneity. The
    scientific meaning of diversity becomes clear
    from the context in which it is used it may
    refer to heterogeneity of species, habitats or
    genes.

8
Species
  • A group of organisms that can interbreed and
    produce fertile viable offspring

9
Kinds of Biodiversity
  1. Biodiversity the amount of biological or living
    diversity per unit area. It includes the
    concepts of species diversity, genetic diversity
    and habitat diversity
  2. Genetic diversity the range of genetic material
    present in a gene pool or population of a species
  3. Species diversity variety among species per
    unit area. Includes both the number of species
    present and their abundance.
  4. Habitat diversity The range of different
    habitats or number of ecological niches per unit
    area in an ecosystem, community or biome.
    Conservation of habitat diversity usually leads
    to conservation of species and genetic diversity

10
Each Species and Process
  • Is key to the overall function of earth
  • In general Diversity Stability
  • Biodiversity is
  • Natures insurance policy against change
  • The source of all natural capital for human use
  • The way chemical materials are cycled and
    purified
  • The end result of millions of years of evolution
    and irreplaceable

11
China
India
Mexico
Philippines
Brazil
Indonesia
Madagascar
Australia
South Africa
The 19 Most Biodiverse countries in the
world. What is the Problem with this?
12
Mediterranean basin
Philippines
Caribbean
Western Ghats and Sri Lanka
Wallacea
New Caledonia
Polynesia and Micronesia island complex
Biodiversity Hotspots need special consideration
13
Hotspots
  • These areas need emergency conservation attention
  • Especially rich in endemic plant and animal
    species (found nowhere else in the world)
  • They cover on 1.4 of world land area
  • Mostly tropical forests
  • Contain 60 of identified terrestrial
    biodiversity
  • 55 of all primates, 22 of all carnivores
  • 1.1 billion people living in poverty near these
    sites
  • 500 million annually would go far to ensure
    their preservation

14
Diversity includes
  • Richness The number of species per sample is a
    measure of richness.
  • ? The more species present in a sample, the
    richer the sample.
  • Evenness A measure of the relative abundance of
    the different species making up the richness of
    an area.

15
Which sample is more diverse?
Flower Species Sample 1 Sample 2
Daisy 300 20
Dandelion 335 49
Buttercup 365 931
Total 1000 1000
Which has a higher richness? Evenness?
16
Quantifiying this Diversity Simpsons Index
  • D N (N 1)
  • ? n (n 1)
  • Where D diversity index
  • N total of organisms of all
    species
  • n of individuals of
    particular species

17
Now practice the simpsons index
Species Number (n) n (n 1)
Woodrush 2
Holly seedlings 8
Bramble 1
Yorkshire Fog 1
Sedge 3
Total (N)
18
Now practice the simpsons index
Species Number (n) n (n 1)
Woodrush 2
Holly seedlings 8
Bramble 1
Yorkshire Fog 1
Sedge 3
Total (N) 15
19
Now practice the simpsons index
Species Number (n) n (n 1)
Woodrush 2 2
Holly seedlings 8 56
Bramble 1 0
Yorkshire Fog 1 0
Sedge 3 6
Total (N) 15 64
15(14) / 64 3.28
20
  • High values of D suggests a stable and ancient
    site
  • A low value of D could suggest pollution,
    recent colonization, or agricultural management
  • Index normally used in studies of vegetation but
    can be applied to comparisons of diversity of any
    species

21
How does diversity exist?
  • Natural Selection survival of the fittest
  • Fitness a measure of reproductive success
  • If all individuals are variable
  • And populations produce large numbers of
    offspring without increase in population size
  • And resources are limited
  • And traits are heritable
  • Then those individuals who are best adapted to
    the environment will survive and pass on their
    genes
  • Gradually the gene frequency in the population
    will represent more of these fit individuals

22
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24
Modern humans (Homo sapiens) appear about 2
seconds before midnight
Recorded human history begins 1/4 second before
midnight
Age of mammals
Age of reptiles
midnight
Insects and amphibians invade the land
Origin of life (3.63.8 billion years ago)
Plants invade the land
First fossil record of animals
Plants begin invading land
noon
Evolution and expansion of life
25
Natural Selection over Time
  • Environmental Pressures select for some genotypes
    over others
  • Alleles resulting in a beneficial trait will
    become more common
  • Heritable traits that increase survival chances
    are called adaptations
  • There are many niches or habitats and roles
    available in the environment
  • As populations adapt they fill new niches and
    over time may develop into new species

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Speciation
  • Certain circumstances lead to the production of
    new species through natural selection
  • Most common mechanism has 2 phases ? geographic
    followed by reproductive isolation
  • 1. Geographic isolation ? groups of a population
    of the same species are isolated for long periods
  • A group may migrate in search of food to an area
    with different environmental conditions
  • Populations may be separated by a physical
    barrier (mountain range, river, road)
  • Catastrophic change by volcano eruption or
    earthquake
  • A few individuals carried away by wind or water
    to new area

29
Speciation 2
  • Reproductive Isolation ? mutation and natural
    selection operate independently on the 2
    populations to change allele frequencies
    divergence
  • If divergence continues long enough genetic
    differences may prohibit (1) interbreeding
    between populations and/or (2) production of
    viable, fertile offspring
  • One species has become 2 through divergent
    evolution
  • For most species this would take millions of
    years
  • Difficult to document prove this process

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31
Consequences of Plate Activity
  • Speciation processes rely on physical separation
    of organisms
  • Plate techtonics
  • can lead to separation of gene pools mountain
    ranges form, faults separating land masses
  • Can link species and land areas e.g. land bridges

32
Consequences of Plate Activity II
  • Plate techtonics generates new habitats
  • Island chains over hotspots Hawaii
  • Mountain habitats Himalayan mountains also
    associated effects on surrounding areas
  • Hydrothermal vent communities
  • Changes climate on land masses continents drift
    into new climate zones ? e.g. antarctica was once
    covered by tropical rainforest now barren polar
    ice fields

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1. Succession effects Diversity
  • Succession gradual establishment or
    reestablishment of ecosystems over time
  • Pioneer species ? Climax species
  • Low diversity at first, few species can tolerate
    harsh conditions (r selected species)
  • Most diverse in middle of succession, slower
    growing species start to fill in
  • Low diversity at the end, climax species often
    strongest competitors (K selected species)
  • Diversity is a function of disturbance ?
    intermediate disturbance hypothesis

35
Exposed rocks
Lichens and mosses
Balsam fir, paper birch, and white spruce climax
community
Jack pine, black spruce, and aspen
Heath mat
Small herbs and shrubs
Time
36
Species diversity
100
0
Percentage disturbance
37
2. Habitat diversity influences species
genetic diversity
  • More complex areas (more diverse habitats) often
    have higher species genetic diversity
  • Ex. Tropical rainforest Coral reef
  • In both cases, high degree of structural /
    spatial complexity
  • Promotes coexistence by niche partitioning
    diversification

38
Harpy eagle
Ocelot
Blue and gold macaw
Producer to primary consumer
Primary to secondary consumer
Squirrel monkeys
Climbing monstera palm
Secondary to higher-level consumer
Katydid
Green tree snake
All producers and consumers to decomposers
Tree frog
Ants
Bromeliad
Fungi
Bacteria
39
45
Emergent layer
Harpy eagle
40
35
Toco toucan
Canopy
30
Height (meters)
25
20
Wooly opossum
15
10
Shrub layer
Brazilian tapir
5
Black-crowned antpitta
0
40
Complex ecosystems with a variety of nutrient
energy pathways provides stability
  • Energy is key to the function of all ecosystems
  • Biogeochemical cycles recycle necessary materials
    through system
  • More pathways for energy matter more stable
  • Insurance against natural or human changes

41
Human activities
  • Modify succession by adding disturbance
  • Logging, Grazing, Burning all prevent natural
    successional processes
  • Fragmenting habitats by development
  • Isolate populations ? more likely to get
    diseases, succumb to local disturbances
  • We simplify ecosystems ? tall grass prairie
    converted to wheat farms ? more vulnerable

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Bromeliad
44
  • Any ecosystems capacity to survive change may
    depend on its diversity, resilience, and inertia
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