Transcript The hierarchy of life

Species
 Species: the different kinds of living things in a
community
 All individuals are like one another, but are distinct from
other groups
 Species are grouped into ________Which are grouped
into families, orders, classes, phyla, kingdoms, and
domains
 The official species name is Latin and has two parts:
It is hard to define a species
 All members that can interbreed and produce fertile
offspring
 Members of different species generally do not breed
 This definition does not work for organisms that do
not mate to produce offspring
 Scientists use other classification methods
 New species arise due to evolution
 Species classifications are changed to reflect this
Populations and biotic communities
 Population: a number of individuals that make up the
interbreeding, reproducing group
 It refers only to individuals of a species in an area
 For example, gray wolves in Yellowstone National Park
 A species would be all gray wolves in the world
 A biotic community (biota): the grouping of
populations in a natural area
 Includes all vegetation, animals, and microscopic
organisms
Species within a biotic community
 The biotic community is determined by abiotic
(nonliving chemical and physical) factors
 Water, climate, salinity, soil
 A community is usually named for its plants
 Vegetation strongly indicates environmental conditions
 Species in a community depend on each other
 The plant community supports the animals
 Populations of different species within a biotic
community constantly interact
 With each other and with the abiotic environment
Pine Forest Community
Ecosystems
 Ecosystem: an interactive complex of biota and the
abiotic environment within an area
 A forest, grassland, wetland, coral reef
 Humans are part of ecosystems
 Ecosystems lack distinct boundaries and are not
isolated
 Species can occupy multiple ecosystems and migrate
between them
 Ecotone: a transitional region between ecosystems
 Shares species and characteristics of both
 May have more or fewer species than the ecosystems
Ecotones
Landscapes and biomes
 Landscape: a cluster of interacting ecosystems
 Biome: a large area of Earth with the same climate and
similar vegetation
 For example, grasslands can be predicted by rainfall and
temperature
 Boundaries grade into the next biome
 Biomes describe terrestrial systems
 Aquatic and wetland ecosystems are determined by
depth, salinity, and permanence of water
 Biosphere: one huge system formed by all living
things
Environmental factors
 Organisms live in the environment with physical,
chemical, and biological factors
 Some factors vary in space and time but are not used
up (temperature, wind, pH, salinity)
 Some factors are consumed by organisms
 Water, nutrients, light, oxygen, food, space
 Factors determine whether a species occupies an area
Optimums, ranges and limits of
tolerance
A fundamental biological principle
 Every species has an optimum range and limits of
tolerance for every abiotic factor
 These characteristics vary between species
 Some species have a broad range
 Other species have a narrower range
 The range of tolerance for a factor affects an organism’s
growth, health, survival, reproduction
 The population density of a species is greatest where
all conditions are optimal
Law of limiting factors
Habitat and niche
Energy changes in organisms
 Breaking bonds in molecules releases energy to do
work
 Oxidation: a loss of electrons
 Usually accomplished by the addition of oxygen (which
causes burning)
 Inorganic compounds are nonflammable
 They have low potential energy
 Production of organic material from inorganic
material represents a gain in potential energy
 Breakdown of organic material releases energy
Producers make organic molecules
 Producers: make high-potential-energy organic
molecules from low-potential-energy raw materials
(CO2, H2O, N, P)
 Chlorophyll in plants absorbs kinetic light energy to
power the production of organic molecules
 Green plants use the process of photosynthesis to
make
 Sugar (glucose—stored chemical energy)
 Using inputs of carbon dioxide, water, and light energy
 Releasing oxygen as a by-product
Within the plant
 Glucose serves three purposes
 It is the backbone for all other organic molecules
 It provides energy to run cell activities (e.g., growth)
 It is stored for future use (as starch in potatoes, grains,
seeds)
 Each stage of the process uses enzymes: proteins that
promote the synthesis or breaking of chemical bonds
Cell respiration
 Consumers: organisms that live on the production of
others
 Obtain energy from feeding on and breaking down
organic matter made by producers
 Respiration: organic molecules are broken down
inside each cell
 Produces energy for the cell to use
 The reverse of photosynthesis
 Oxygen is consumed
 Occurs in plants and animals
One-way flow of energy
 Most solar energy entering ecosystems is absorbed
 Heats the atmosphere, oceans, and land
 2–5% is passed through plants to consumers
 All energy eventually escapes as heat
 Entropy is increased
 Re-radiated into space
 Energy flows in a one-way direction through ecosystems
 Light from the Sun is nonpolluting and nondepletable
 In contrast, nutrients are recycled and continually reused
The cycling of matter in ecosystems
 Biogeochemical cycles: circular pathways of
elements involving biological, geological, and
chemical processes
 The carbon cycle: starts with the reservoir of carbon
dioxide in the air
 Becomes organic molecules in organisms
 Carbon is respired by plants and animals into the air or
is deposited in soil
 Photosynthesis in oceans moves CO2 from seawater
into organisms
 Respiration returns inorganic carbon to seawater
CO2 in atmosphere
5
Burning
Carbon Cycle
3
Photosynthesis
Cellular respiration
1
Higher-level
consumers
Wood
and
fossil
fuels
Plants, algae,
cyanobacteria
Primary
consumers
2
Decomposition
Wastes; death
Decomposers
(soil microbes)
4
Detritus
Plant litter;
death
The phosphorus cycle
 Mineral elements originate in rock and soil minerals
 A shortage of phosphorus is a limiting factor
 Excessive phosphorus can stimulate algal growth
 As rock breaks down, phosphate is released
 Replenishes phosphate lost through leaching or runoff
 Organic phosphate: incorporated into organic
compounds by plants from soil or water
 Cycles through the food chain
 Broken down in cell respiration or by decomposers
 Enters into chemical reactions with other substances
6
Uplifting
of rock Weathering
of rock
3
Phosphates
in rock
Runoff
Animals
Plants
1
Assimilation
2
Phosphates
in solution
5
Rock
Precipitated
(solid) phosphates
Detritus
Phosphates
in soil
(inorganic)
4
Decomposition
Decomposers
in soil
The nitrogen cycle
 Is a unique cycle
 Bacteria in soils, water, and sediments perform many
steps of the cycle
 Nitrogen is in high demand by aquatic and terrestrial
plants
 Air is the main reservoir of nitrogen (N)
 most organisms can not use it
Plants take up nitrogen
 Plants in terrestrial ecosystems (“non-N-fixing
producers”)
 Take up nitrogen as ammonium (NH4) and incorporate
it into proteins and nucleic acid compounds
 The nitrogen moves through the food chain to
decomposers, releasing nitrogen wastes
 Soil bacteria (nitrifying bacteria) convert ammonium
to nitrate to obtain energy
 Nitrate is available for plant uptake
 Nitrogen fixation: bacteria and cyanobacteria can
use N and produce compounds
Means of nitrogen fixation
 Bacteria (genus Rhizobium) live in legume root nodules
 The legume provides the bacteria a place to live and food
 It receives a source of nitrogen in return
 Nitrogen enters the food chain from the legumes
 Three other processes “fix” nitrogen
 Atmospheric nitrogen fixation: lightning
 Industrial fixation: in fertilizer manufacturing
 Combustion of fossil fuels: oxidizes nitrogen
 Industrial fixation and fossil fuels release nitrogen oxides,
which are converted to nitric acid (acid precipitation)
Denitrification
 A microbial process in soils and sediments depleted of
oxygen
 Microbes use nitrate as a substitute for oxygen
 Nitrogen is reduced (it gains electrons) to nitrogen gas
 Released into the atmosphere
Figure 37.21 The nitrogen cycle
Nitrogen (N2) in atmosphere
8
Animal
Plant
6
Assimilation
by plants
1
5
Denitrifiers
3
Nitrates
in soil
(NO3)
Nitrogen-fixing
bacteria in
root nodules
Detritus
Decomposers
4
Nitrifying
bacteria
Free-living
nitrogen-fixing
bacteria
7
Ammonium (NH4)
in soil
2
Comparing the cycles
 Carbon is mainly found in the atmosphere
 Directly taken in by plants
 Nitrogen and phosphorus are limiting factors
 All three cycles have been sped up by human actions
 Acid rain, greenhouse gases, eutrophication
 Other cycles exist for other elements (e.g., water)
 All go on simultaneously
 All come together in tissues of living things
Dynamics of natural populations
 Population: a group of members of the same species
living in an area
 Community: populations of different species living
together in an area
 Populations grow with births and immigration
 They decline with deaths and emigration
(Births + Immigration) – (Deaths + Emigration)
= Change in population number
Dynamics of natural populations
 Population: a group of members of the same species
living in an area
 Community: populations of different species living
together in an area
 Populations grow with births and immigration
 They decline with deaths and emigration
(Births + Immigration) – (Deaths + Emigration)
= Change in population number
Population growth
 Population growth: change in population
 Equilibrium: births + immigration are equal to deaths
+ emigration
 Often, population growth is not zero
 Population growth rate: amount the population has
changed divided by the time it had to change
 Population growth curves: graph how populations
grow; used to find
 How fast a population could grow
 How many individuals there are now
 What the future population size could be
Exponential growth
 Each species can increase its population
 With favorable conditions
 Exponential increase: does not add a constant
number of individuals for each time period
 The doubling time remains constant
 For example, it takes 2 days to go from 8 to 16
individuals, as well as from 1,000 to 2,000 individuals
 Such growth is called an “explosion”
 The population continues to grow and then dies off due
to limiting resources
 J-curve: the curve of exponential growth
Exponential growth of rabbits
Population size (N)
500
450
400
350
300
250
200
150
100
50
0
0 1 2 3 4 5 6 7 8 9 10 11 12
Time (months)
Logistic Growth and carrying
capacity
 Logistic growth: some process slows growth so it
levels off near carrying capacity (K)
 Results in an S-shaped curve
 It levels off at K
 As the population approaches K, growth slows
 The population remains steady and growth = 0
 The maximum rate of population growth occurs halfway
to K
Breeding male fur seals
(thousands)
Logistic growth of a population of fur seals
10
8
6
4
2
0
1915
1925
1935
Year
1945
Biotic potential vs. environmental
resistance
 Biotic potential: the number of offspring (live births,
eggs, or plant seeds and spores) produced under ideal
situations
 Measured by rate at which organisms reproduce (r)
 Varies tremendously from less than 1 birth/year (some
mammals) to millions/year (plants, invertebrates)
 Recruitment: survival through early growth stages to
become part of the breeding population
 Young must survive and reproduce to have any effect on
population size
Environmental resistance
 Abiotic and biotic factors cause mortality (death)
 Prevents unlimited population growth
 Environmental resistance: the biotic and abiotic
factors that may limit a population’s increase
 Biotic: predators, parasites, competitors, lack of food
 Abiotic: unusual temperatures, moisture, light, salinity,
pH, lack of nutrients, fire
 Environmental resistance can also lower reproduction
 Loss of suitable habitat, pollution
 Changed migratory habits of animals
Reproductive strategies: r-strategists
Reproductive strategies: K-strategists
Life histories
 Life history: progression of changes in an organism’s life
 Age at first reproduction, length of life, etc.
 Visualized in a survivorship graph
 Type I survivorship: low mortality in early life
 Most live the bulk of their life span (e.g., humans)
 Type III survivorship: many offspring that die young
 Few live to the end of their life (oysters, dandelions)
 Type II survivorship: intermediate survivorship pattern
(squirrels, coral)
 K-strategists have a Type I pattern; r-strategists show Type
III
Percentage of survivors (log scale)
100
I
10
II
1
III
0.1
0
50
Percentage of maximum life span
100
Predictable pattern in species
 There is a predictable pattern to the way human
activities affect species
 r-strategists become pests when humans change an
area
 Houseflies, dandelions, cockroaches increase
 K-strategists become rarer or extinct with change
 Eagles, bears, and oaks decline
Community interactions
Species interactions
 The most important relationships
 Predation, competition, mutualism, commensalism
 Amensalism: one species is unaffected, the other is
harmed (0−)
 For example, an elephant stepping on a flower or plants
produce chemicals for defense against herbivory that
inadvertently harms other plants
 It is theoretically possible to have a (00) relationship
 It has no name
Introduction to ecosystems
 In 1988, lightning started fires in Yellowstone National
Park
 165,000 acres were burned in one day
 National Park Service policies have changed over time
 In the early years, all fires were extinguished
 Before 1988, only fires that threatened human
habitations were extinguished
 This fire started a great controversy over this policy
 Snow in September finally put the fires out
Fire in Yellowstone
Yellowstone recovered from the
1988 fire
 The fires burned 36% of the park
 Burned and unburned areas were interspersed
 Within 2 weeks, grasses and other vegetation sprouted
 Within a year, vegetation covered the burned areas
 Bison and elk fed on the new vegetation
 Within 25 years, plant and animal diversity will have
completely recovered in the burned areas
 Fire is vital to many ecosystems
 It may even impact evolution
Lodgepole pines growing back in
the burned area of Yellowstone
Bison in Yellowstone
Characteristics of ecosystems
 Yellowstone National Park (founded in 1872) is part of
the Greater Yellowstone Ecosystem
 Because of its unique features, it is a World Heritage Site
and International Biosphere Reserve
 Ecosystems contain communities of interacting
species and their abiotic factors
 They function on different scales
 It’s hard to delineate fixed boundaries
Scientists study ecosystems
 Biomes: ecosystems having similar vegetation and
climactic conditions
 Greater Yellowstone Ecosystem belongs to the northern
temperate forest biome
 Scientists study ecosystem properties
 Trophic levels
 Productivity
 Consumption
Trophic levels
 During photosynthesis, plants use the Sun’s energy
 Producing chemicals from carbon dioxide and water
 Plants are eaten by predators (a grasshopper, mouse,
etc.)
 These animals are eaten by other predators
 Food chain: describes where energy and nutrients go
as they move from one organism to another
 Energy moves “up” the food chain
 Not all energy and nutrients are passed to other levels
 Food web: interconnection of food chains to form
complex webs of feeding relationships
Trophic level
Quaternary
consumers
Hawk
Snake
Killer whale
Tertiary
consumers
Tuna
Mouse
Secondary
consumers
Herring
Grasshopper
Primary
consumers
Zooplankton
Plant
Producers
A terrestrial food chain
Phytoplankton
An aquatic food chain
Quaternary,
tertiary,
and secondary
consumers
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Primary
consumers
Producers
(plants)
Trophic categories
Producers are essential to every
ecosystem
 They capture energy from the Sun or chemical reactions
 Converting CO2 to organic matter
 Most producers are green plants
 Chlorophyll: a green pigment that captures light energy
 Range in size from microscopic bacteria to gigantic trees
 Every major ecosystem has producers
 Chemosynthesis: some bacteria use energy in inorganic
chemicals to form organic matter from CO2 and water
 Primary production: production of organic matter
through photosynthesis and growth of producers
Consumers
 Organisms feed on organic matter for energy
 Animals, fungi (mushrooms, mold, etc.), most bacteria
 Range in size from plankton to blue whales
 Divided into subgroups according to their food source
 Primary consumers (herbivores): feed on producers
 Secondary consumers: feed on primary consumers
 Third (tertiary), fourth (quaternary), or higher levels
 Carnivores: secondary or higher-order meat eaters
 Omnivores: feed on both plants and animals
 Animals can occupy various levels, depending on the
food
Decomposers
 Detritus: dead plant material (leaves, etc.), fecal
wastes, dead bodies
 Most energy in an ecosystem goes through this food web
 Detritus is organic and high in potential energy for
 Decomposers
 Scavengers (vultures): break down large pieces of matter
 Detritus feeders (earthworms): eat partly decomposed
matter
 Chemical decomposers (fungi and bacteria): break down
matter on the molecular scale
Limits on trophic levels
 Terrestrial ecosystems usually have three or four
trophic levels and rarely five
 Biomass: the total combined (net dry) weight of
organisms
 Each higher trophic level has about 90% less biomass
 One acre of grassland has 907 kg (2,000 lbs)
 It has 90.7 kg (200 lbs) of herbivores
 It has 9.7 kg (20 lbs) of primary carnivores
 Biomass pyramid: the different levels of producer
and consumer mass
Tertiary
consumers
10 kcal
Secondary
consumers
100 kcal
Primary
consumers
Producers
1,000 kcal
10,000 kcal
1,000,000 kcal of sunlight
The flow of energy in ecosystems
 In most ecosystems, sunlight is the initial source of energy
 Primary production (production of organic molecules) is
only 2% of the incoming solar energy
 Although small, it’s enough to fuel all life
 On average 10% energy is available to each trophic level
 Standing-crop biomass: the actual biomass of primary
producers in an ecosystem at any given time
 Not always a good measure of productivity
 Biomass and primary production vary greatly
 Forests have large biomass
 Grasslands have high primary production
From ecosystems to biomes
 Broad ecosystem patterns translate into a predictable
set of organisms that live under particular conditions
 Different regions have distinct biotic communities
 Creating variety in ecosystems, landscapes, and biomes
 A biome: a large geographical biotic community
 Controlled by climate
 Is named after the dominant vegetation
 Has fuzzy boundaries
 Aquatic areas are not called biomes
 But they function similarly
The role of climate
 Climate: a description of the average temperature and
precipitation (weather) of a region
 Climates vary widely
 Equatorial areas: warm, high rainfall, no seasons
 Above and below the equator: temperatures become
seasonal (warm/hot summers, cool/cold winters)
 Toward the poles: longer and colder winters
 Colder temperatures are also found at higher
elevations
30N
Tropic of
Cancer
Tropic of
Capricorn
Equator
30S
Key
Tropical forest
Chaparral
Coniferous forest
Savanna
Temperate grassland
Arctic tundra
Desert
Temperate
broadleaf forest
Polar ice
High mountains
(coniferous forest
and alpine tundra)
Effects of precipitation on biomes
 Precipitation varies widely in different regions
 From almost 0 to over 250 cm (100 in.)/yr
 It can be evenly distributed throughout the year or
concentrated in certain months (wet and dry seasons)
 A given climate supports species that can tolerate the
temperature and precipitation levels of the area
 Highest densities occur where conditions are optimal
 A species is excluded where any condition is beyond its
range of tolerance
Biome examples
 Individual ranges of tolerance to temperature and
precipitation determine where a species can live
 Species’ distributions describe a biome’s placement
 Six major types of biomes exist
 Rainfall effects are primary in determining biomes
 Temperate deciduous forest: rainfall of 72–200 cm
(30–80 in.)/yr
 Grassland (prairie) biome: rainfall is less or seasonal
 Desert biome: rainfall is less than 25 cm (10 in.)/yr
The effects of temperature on
biomes
 Temperature effects are superimposed on rainfall
effects
 It determines the kind of forests in an area with
75 cm (30 in.) or more of rainfall per year
 Tropical rain forests have broad-leaved evergreens
that cannot tolerate freezing
 Deciduous trees tolerate freezing by dropping their
leaves and becoming dormant
 Coniferous forests tolerate the harsh winters and short
summers of northern regions
Biomes with little precipitation
 Permafrost: permanently frozen subsoil
 Prohibits tree growth because their roots cannot
penetrate the soil
 Tundra biome: has grasses, clover, and other small
plants that grow above the permafrost
 Desert: any region with less than 25 cm (10 in.) of
rain/yr
 Hot deserts have different species than cold deserts
Aquatic systems
 Aquatic systems have major categories
 But are not called biomes
 Aquatic and wetland ecosystems are determined by
depth, salinity, and permanence of water
 Lakes, marshes, streams, rivers, estuaries, bays
 Ocean systems
 Aquatic systems can be viewed as ecosystems
 Or part of landscapes
 Or as major biome-like features (seas, oceans)
High tide
Low tide
Pelagic realm (open water)
Sea star
(to 33 cm)
Intertidal
zone
Man-of-war
(to 50 m
long)
Oarweed (to 2 m)
Brain coral
(to 1.8 m)
Phytoplankton
Turtle
(60180 cm)
Zooplankton
Blue shark (to 2 m)
Photic
zone
200 m
Continental shelf
Sponges (1 cm1 m)
Sperm whale (1020 m)
Sea pen
(to 45 cm)
Benthic realm
(seafloor from continental
shelf to deep-sea bottom)
Octopus
(to 10 m)
“Twilight”
Hatchet fish
(260 cm)
Gulper eel
(to 180 cm)
Sea spider
(190 cm)
1,000 m
Aphotic
zone
Rat-tail fish (to 80 cm)
Angler fish
(45 cm2 m)
Brittle star
(to 60 cm)
Glass sponge
(to 1.8 m)
Sea cucumber
(to 40 cm)
Tripod fish
(to 30 cm)
No light
6,000
10,000 m
Freshwater biomes fall into two broad groups:
flowing water biomes (rivers and streams) and standing
water biomes (lakes and ponds).
Photic
zone
Benthic
realm
Aphotic
zone
Ecosystem responses to
disturbance
 Natural ecosystems operate in dynamic, changing ways
 Disturbance: a significant change that kills or displaces
many community members
 Ecological succession: transition from one biotic
community to another
 Pioneer species: colonize a newly opened area first
 Species can create conditions favorable to other species and
less favorable to them
 Climax is the “final” community but even these communities
experience change if new species are introduced or old ones
are removed
 Patches of disturbance open space for new growth
Primary succession
Secondary succession
Aquatic succession
 Natural succession also takes place in lakes and ponds
 Soil particles erode from the land and enter the water
 Aquatic vegetation provides detritus that also fills the
pond or lake
 Terrestrial species advance and aquatic species move
further into the lake
 The climax ecosystem can be a bog or forest
 Disturbances (e.g., drought, flood) can send succession
back to an earlier stage
Human values and sustainability
 Natural ecosystems are models of sustainability
 We depend on them for goods and services (ecosystem
capital)
 We are threatening their sustainability
 Humans use energy that flows through ecosystems
 Converting forests and grasslands into agricultural
ecosystems
 We appropriate 40% of global net primary
productivity
 For agriculture, grazing, forestry, houses, roads, etc.
 Humans are the dominant biological force on Earth and
ecosystems have become degraded or destroyed
Restoration ecology
 Consists of developing a model of the desired
ecosystem
 Designing and implementing a plan for restoration
 Stating clear standards to evaluate progress
 Monitoring the plan
 Developing strategies for long-term protection and
maintenance of the system
 We should restore ecosystems
 For aesthetic reasons, human use, other species
 Nature has value separate from humans