Biodiversity in Ecosystems

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Biodiversity in Ecosystems

• IB syllabus 3.1
• AP syllabus
• Ch 5,

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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.

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• 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.

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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

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• 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.

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vocabulary

• Biodiversity
• Diversity
• Diversity index
• Genetic Diversity
• Habitat diversity
• Isolation
• Plate Tectonics
• Species Diversity

• Speciation
• Species

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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.

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Species

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

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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

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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

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China
India
Mexico
Philippines
Brazil
Indonesia
Madagascar
Australia
South Africa
The 19 Most Biodiverse countries in the
world. What is the Problem with this?
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Mediterranean basin
Philippines
Caribbean
Western Ghats and Sri Lanka
Wallacea
New Caledonia
Polynesia and Micronesia island complex
Biodiversity Hotspots need special consideration
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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

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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.

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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?
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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

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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)
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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
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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
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• 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

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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

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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
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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

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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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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
  

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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

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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
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Species diversity
100
0
Percentage disturbance
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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

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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
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Emergent layer
Harpy eagle
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Toco toucan
Canopy
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Height (meters)
25
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Wooly opossum
15
10
Shrub layer
Brazilian tapir
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Black-crowned antpitta
0
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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

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