LECTURE 13: POPULATION ECOLOGY &

ECOSYSTEM

BASIC GENETICS AND INHERITANCE1. Introduction2. Basic Genetics &

Inheritance– Gene– Chromosome– Loci– Allele– Features– Gametes– Zygote– Diploid

– Dominant & Recessive

– Homozygous– Heterozygous

3. Review4. Inheritance

– Principle of Inheritance

– A Punnett square5. Genetic Problems6. Genetic

engineering

Population Ecology

Ecology is the study of interactions among organisms

and their environment

• Not concerned with individuals• Populations - same area, same time• Population ecology - looks at the

dynamics of populations that are similar between species

• Population density - number of individuals of a given species in a specific area at a given time

• Range - geographic area or limit of a population• Dispersion - frequency or patterns of individuals

within a range:• uniform• random• clumped

Population change• Growth rate = births - deaths

+immigration - emigration• Doubling rate (time it takes for a

population to double) = 0.7/growth rate (see page 911)

• Biotic potential = maximum rate of population growth given ideal circumstances

Limits on growth• Environmental resistance - combination

of the limiting factors and effects• Limiting Factors - any resource or

requirement that acts to limit population when in short supply

• Carrying capacity (K) - the greatest population that can be maintained indefinitely by a given system or place

Density dependent factors• As population increases the rate of

growth is slowed by density dependent factors either by increasing the death rate or decreasing the birth rate

• predation, disease, intraspecifc (within a species) competition and interspecific competition

Density independent factors

• Weather events• natural disasters

Survival tactics - reproduction• r strategies - (r = growth rate) - small

body size, large brood, short life span, may be opportunistic and found in disturbed or variable environments

• K strategies - (K=carrying capacity) - large body small brood, long life, care for young, constant or stable environments

Human population growth• 1800 human population reaches 1 billion• 1930 - in 130 years 2 billion• 1960 - in 30 years 3 billion• 1975 - in 15 years 4 billion• 1987 - in 12 years 5 billion• 1999 - in 12 years 6 billion

What are the density dependent limits to growth

acting on human population?

Demographic transition• Preindustrial stage - high birth and death

rates - slow population growth • transitional stage - lower death rate but birth

rate remains high - rapid population growth• industrial stage - birth rate declines - rate of

growth slows• post industrial stage - low birth and death

rates

Communities of organisms• Producers - autotrophs• Consumers - heterotrophs• primary and secondary• Decomposers - heterotrophs

No organism lives in isolation. Every living thing is part of a community.

• Predation - pursuit and ambush• Defenses - camoflage, chemical

defense, mimicry - (batesian mimicry or mullerian mimicry)

Mutualism

• A symbiotic relationship• both partners benefit

– rhizobium bacteria and plants– pilot fish and sharks?

Commensalism

• One benefits , the other is neither harmed nor helped– epiphytes– sea ducks and sting rays

Parasitism

• Parasite and host• pathogen - parasite that causes disease

Niche

• The ecological role of an organism is its niche

• fundamental niche- potential niche• realized niche- actual• interspecific competition leads to

competitive exclusion - absolute overlap cannot exist in nature

Diversity in communities

• Isolated or places with harsh environments have less diversity

• edge effect - diversity is usually greatest at the margins

• old communities (tropical rainforests) tend to be more diverse than new communities (Canadian shield, artic)

Succession• Primary succession - change in species

composition over time in a habitat not previously inhabited by organisms

• Pioneer community - first community to appear

• Secondary succession - change in species composition over time in a habitat already modified by previous organisms

• Climax community -

Ecosystems and Environment

Biogeochemical cycles

• All materials flow through the environment over time- materials cycle through the environment

Energy

• Energy flows through the environment• Sunlight to chlorophyll to photosynthesis to

sugars to plant biomass to….• Food chains - energy passes from one

organism to another - it is a one way trip- energy passed through the environment in a linear fashion- unlike materials

Food chains

• Trophic levels• available energy and biomass decrease at

each trophic level • Gross primary productivity - rate at which

energy is captured and stored in plant tissues

• Net primary productivity - energy after plant’s requirements

Major ecosystems

• Biomes - large distinct ecosystem– tundra– tiaga or boreal forest– temperate rainforest– temperate deciduous forest– temperate grasslands– chaparral

Biomes

– Deserts– savanna– tropical rainforests

Aquatic ecosystems• lakes and ponds

– littoral zones - nearest to shore– limnetic zones - open water– profundal zone - no light

• marine– intertidal - very productive– pelagic - open ocean– euphotic - light is present (100m)– neritic - 100m to 200m– oceanic - no light

Stratification in water

• In summer warm layers on top, colder at the bottom, separated by thermocline

• in fall, water turns over and some mixing between layers occurs

• in winter cold at top, warmer at bottom• in spring another turnover!• Spring turnover stimulates algae growth...

Environmental Issues

• Habitat destruction• pollution• foreign or exotic species• deforestation• global warming• ozone depletion

REVIEW

2. Colorblindness

of• A heterozygous

3. Sex Determination

C• The major pieces).

• Genes

6. Hemophilia

7. Gene Therapy

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• group