Ecology and HumansChapters 3, 4 (up to biomes), 5, 8

Levels of Organization in Ecology Ecology is the study of interactions among organisms and

between organisms and their environment

Species/Organisms Populations: in population ecology, scientists study the

dynamics of population change and the factors that affect distribution/abundance of organisms (Chapter 3)

Communities: in community ecology, scientists study patterns in species diversity and all interactions (Chapter 4)

Ecosystems: in ecosystem ecology, scientists study the flow of energy and nutrients, both the living and non-living components of a system (Chapter 5)

Biomes Biosphere

Population Ecologyin population ecology, scientists study the dynamics of population change (natural selection and evolution) and the factors that affect distribution/abundance of organisms (Chapter 3)

Evolution and Natural Selection How are these two terms different? Darwin versus Wallace Evolution (mutation) leads to adaptation and

adaptive traits in a population Changes can result in no change, positive change,

or negative change Natural selection acts on changes

Selection can be Directional Stabilizing Disruptive

Take a minute to draw a sketch of these three trends

Evolution and Natural Selection The environment can

influence selection Convergent Evolution Divergent Evolution

Selection can be seen in our everyday lives Ex: Breeding in dogs,

artificial selection in plants

Biological diversity is a result of evolution 100 million species in

world

Speciation Generation of

new species can occur in several ways Allopatric

Speciation (main mode)

Sympatric Speciation (sym….same)

Fossils and Extinction Fossils can show us many things

Existence of life on Earth for 3.5 B years Evolution of organisms Number of exiting species generally increases Most species are now extinct Several mass extinctions have occurred

Background extinction rate 6th mass extinction is occurring now

Phylogenetic trees can be used to trace the divergence of organisms

Resources needed by organisms

Habitat Habitat use Habitat selection

Niche Specialists versus

Generalists Fundamental

niche versus realized niche

Characteristics of populations The following characteristics can be used to

predict the future dynamics of a population Population Size Population Density

What are the advantages of high/low density? Population Distribution

Random, Uniform, Clumped Take a minute, to sketch a diagram of these three

distributions and an example of each Sex Ratio Age Structure Birth and Death Rates

Can be used to develop survivorship curves

Survivorship Curves Take a minute to graph Type I, II, and III

survivorship curves and list an example of species of each curve, note which are K-selected and which are R-selected

Growth is determined by Births (natality) Deaths (mortality) Immigration Emigration

How can you calculate the natural rate of population growth?

How can you calculate the population growth rate?

Factors that influence population growth Exponential growth is seen in populations that grow by a

fixed percent each year Take a second to sketch a graph of this type of curve and give

an example of an organism In reality, limiting factors will prevent a population from

growing forever, this type of scenario is shown in a logistic growth curve Populations rise sharply at first, but them begin to level off as

limiting factors become stronger, the force of these factors is called the environmental resistance and stabilizes the population at its carrying capacity

Take a second to sketch a graph of this type of curve and give an example of an organism

Density-dependent factors versus density-independent factors; both can be limiting factors and create variations in a growth curve

Carrying capacity is not set in stone

Community Ecologyin community ecology, scientists study patterns in species diversity and all interactions (Chapter 4); changes in populations can influence the composition of the community

How do species interact? Competition (- -)

Intraspecific versus Interspecific Competitive exclusion or species coexistence Resource partitioning and character displacement: role of

natural selection Predation, Parasitism (*S), Herbivory (+ -)

Predation can drive cyclical population dynamics, take a second to graph this type of relationship and give an example

Coevolution, evolutionary arms race Mutualism (*S) (+ +)

Mycorrhizae Digestion

Amensalism (- 0) Commensalism (*S)(+ 0) *S=Symbiosis: a close relationship between two organisms

Energy flows through ecosystems Types of organisms: producers, consumers,

detrivores, decomposers Trophic level: literally means feeding level,

traced through food web or food chain Energy, biomass and number of organisms

decrease a higher trophic levels

10% Rule1) The 10% rule states that only 10% of energy is transferred between each trophic level. It is argued that this percentage is an inappropriate measurement. Assume that the producers in this diagram obtain 3,745 kcals of energy through the processes of photosynthesis. How much energy would the secondary consumers receive if 8.2% of energy is transferred between tropic levels?

2)Using the ideas of energy transfer through trophic levels, number of organisms, and biomass, explain why vegetarians have a smaller energy footprint than a person who eats meat.

Role of organisms in communities Keystone species

What is a keystone in architecture? Trophic cascade

High level predators can keep levels of secondary consumers in check, which promotes the success of the producers

Ecosystem engineers Physical changes in the ecosystem

Ex: dams, aeration of soil Affecting the environment

Ex: moving seeds around, filtering the water

Disturbances in the ecosystem Resistance versus resilience versus

permanent change Succession

Primary succession: think glaciers, volcanoes, anything that exposés rock and sand Pioneer species: most commonly liches that can

break down the stone and create new soil Secondary succession: think fires, hurricanes,

logging, farming, anything that removes the majority of living things

Both types of succession will lead to climax communities

How stable are communities? Clements (communities) versus Gleason

(populations) Most people now agree with Gleason, populations

can come and go from communities Ecologists will study how conditions in different

stages of succession can lead to other stages Phase shifts/Regime shifts can sometimes occur

if keystone species are lost, declining populations, or major environmental changes Invasive species can have a major role in changing

communities May be missing limiting factors

Restoration ecology/Ecological restoration

Ecosystem Ecologyin ecosystem ecology, scientists study the flow of energy and nutrients, both the living and non-living components of a system (Chapter 5), this study focuses on systems including the lithosphere (rocks), atmosphere (air), hydrosphere (water), and biosphere (living things). It also focuses on ecosystem services that we rely upon.

Environmental Systems Systems are networks of relationships among parts that interact with

and influence each other through the exchange of energy, matter and information

Feedback loops: a systems output can also create input for a system Negative feedback loop (you want negative test results in the

doctors office): output brings the system back to a starting point, and is therefore stabilized, these are stable systems and the only ones that can be sustained over a long period of time (dynamic equilibrium, homeostasis) More prey increased the number of predators, which in turn

decrease the number of prey Positive feedback loops: drive the change to a further extreme

Melting ice decreases the amount of sunlight reflected from the planet, increasing the temperatures and melting more ice

It is hard to understand feedback without looking at the larger systems because properties emerge at different levels If a property emerges at the ecosystem level, looking only at a

single population may not allow you to see the loop

Example of interactions in a system (hydrosphere) There is a dead zone in the Gulf of Mexico due to

hypoxia, it is more easily understood if we look at entire area of land that drains into the gulf, the river’s watershed

As nutrients from farmers fertilizers and waste water treatment facilities enter the watershed, the drive the growth of phytoplankton, which in turn increases the number of consumers, when these organisms die and sink to the bottom of the water, bacteria populations grow quickly, these bacteria use cellular respiration to break down their food, consuming oxygen and creating hypoxia for fish and other organisms living in lower regions of the water

This process is called eutrophication and is considered to be a negative feedback loop

Ecosystems Arthur Tansley was the first to recognize that

living and nonliving entities interact Energy flows in one direction, matter is cycled Sketch an image that shows the flow of energy

and the cycling of matter through trophic levels Nutrients tend to be limiting factors in marine

systems Macronutrients are required in large amounts

(nitrogen, carbon, phosphorus) Phosphorus is more limiting in freshwater while

nitrogen is more limiting in ocean waters Micronutrients are necessary, but needed in small

amounts

Primary Productivity Energy is converted to biomass

Starting with producers, photosynthesis creates energy in the chemical bonds of sugar, this energy is the gross primary production

Energy that remains after producers complete cellular respiration is the net primary production, this is what will become biomass The gross productivity of the producers in an ecosystem is

5,327kcals of energy. Producers in this system will use 300kcals of energy for cellular respiration. What is the net primary productivity of this system?

The overall rate at which energy is produced is productivity

Secondary Productivity The biomass generated by consumers after eating

producers is known as secondary production In the previous system, 10% of energy is passed

between trophic levels. It takes 350kcals of energy to support every 100g of biomass in primary consumers. The average consumer in the system has a mass of 400g, how many primary consumers can be supported in this ecosystem?

Human currently use approximately ¼ of the Earth’s net primary productivity, why could this lead to a problem that could topple food chains/webs?

Studying Ecosystems Geographic Information System (GIS) is used to

create a picture of the landscape being studied Boundaries are not firm, areas where ecosystems

interact are called ecotones Landscape ecology allows scientists to study how

structures in the landscape affected organisms Patches are spread in a mosaic Populations that stay within patches, but could move

and mate within the patches are called metapopulations,

If organisms can not move between patches, extinction is a greater possibility, so this research is important to conservation biologists

Modeling is also used to represent complex relationships seens in ecosystems

Ecosystem Services(you will want to memorize and use these throughout the course, you will need to know them for the AP test!)

Forming soil, preventing soil erosion Purifying water Purifying air Regulating oxygen and other atmospheric gasses Storing water Protect against floods Pollinating plants we eat Removing toxins from soil, water and air Controlling pests Provides habitats Provides medications, pets, plants, genes Breaking down waste products Stabilize the climate Recreation Aesthetic enjoyment

Biogeochemical Cycles Unlike energy, nutrients cycle through an

ecosystem Nutrients are said to move from one reservoir

(pool) to another, and spend a varying amount of time in each (residence time)

The rate at which nutrients move is called flux Reservoirs that release more than they accept

are called sources, those that accept more are called a sink

Human activities have changed fluxes which may cause negative and/or positive feedback loops

Demography/Human PopulationsDemography is studying the statistical changes of human populations through the application of principles of population ecology

How did we get here? 7B+ humans (1 million x 1,000 = 1 billion) Exponential growth: increasing in a quantity by a

fixed percentage per unit of time Global growth rate peaked in the 1960’s and has

declined since then Currently grows at 1.2% (this seems small)

Calculating Growth Rate We can roughly estimate the doubling

rate of human populations with some knowledge of how populations grow Human growth is exponential (logrithmic) 100 x .7 = ln 2

Therefore, we can use 70 as a shortcut! If you know the growth rate, you can figure

out how many years it will take for the population to double China’s population growth rate is 1.2

70/1.2=58.3 ln2/1.2=.578x100=57.8

Is this a problem? Malthus and Ehrlich Food production has balanced rapid

growth in recent decades What would cornucopians think of this? What would environmental scientists say?

Can we maintain quality of life for all people?

How do the views of Asian governments differ from those of European governments on this topic?

Demographic transitionsLife Expectancy change due to living conditions (healthcare, sanitation, food supplies, need for labor) that can be linked to demographic transitions Pre-industrial stage

High death and birth rates

Relatively stable population

Industrialization Low death, high birth

rates Industrial Stage

Low death, falling birth rates

Post-Industrial Stage Low birth and death

rates Population may be

impacted by immigration

IPAT(S) ModelThe IPAT model offers us a way to measure the impact human population may have on the Earth.

I = P x A x T x S I= impact on environment P= population A= affluence T= technology S?= sensitivity of environment

1) Name one way that technology could increase the impact on the environment and one way it could decrease the impact on the environment.

2) According to this equation, would an arid region of southeastern China where plants grow slowly be more or less impacted by increasing affluence than a moist region where crops are plentiful?

Studying Human Populations Demography: can be used to predict what will

happen to populations and potential environmental impacts of populations Population Size

Doesn’t really tell us the entire story, need other factors

Density/distribution of population Human populations tend to be clumped (draw a quick

sketch of this), this means environmental impacts will be greater in some areas than others

Age structure of population Sex Ratio of population Rates of birth, death, immigration, emigration

Interpreting age structure diagrams Draw a sketch of an increasing, stable, and

decreasing population (assume that the ratio of males to females is around 50:50)

Interpret the following graphs:

Growth versus total population What does this graph show us?

Demographics are linked to society Fertility Rates

Total fertility rate: number of children an average woman has in her lifetime, should not fall below 2.1 Replacement fertility: each couple only having 2 children (2.1

actually) Natural rate of population change (only birth versus death

rates) is becoming a problem in Europe Empowering woman

Fertility rates drop when woman have access to birth control Population policies

Most countries do not have a firm policy at this point, but encourage reproductive rates at or below 2.1

Poverty 99% of the next billion people will be born in developing

nations More than 82% of people live in developing nations

Demographics are linked to society Consumption/Affluence

Humans are living with a 30% overshoot in our ecological footprint

1 American = 4.5 Chinese = 10 Indians = 19 Afgans Wealth Gap

HIV/AIDS Some regions still have increasing death rates

Economic repercussions Demographic fatigue: overwhelming challenges faced by

countries including Losing young and productive members of society to disease Educating/finding jobs for young people

Population Goals/Sustainable Development United Nations Millennium Declaration: sets forth 8 goals for

society http://www.un.org/millenniumgoals/