1. Chapter 5 Biodiversity, Species Interactions and Population Control

2. Species Interact in major ways
Interspecific competition – 2 or more species interact to gain access to limited resources
Predation – prey/predator
parasitism - parasite/host
Mutualism – benefits both species
Commensalism – benefits one species , no effect on the other

3. Cyclic changes – sharp increases in number followed by seemingly periodic crashes
Wolves controlling deer and moose populations
Sheep and rabbits controlling plant growth
Role of predation

4. Competition for resources
the greater the overlap the more intense the competition
Resource partitioning –specialized traits allow species to use shared resources at different times
Competitive exclusion – intense copetition between 2 equal species, both suffer (one more than the other) by having reduced access to resources

5. Population Dynamics
characteristics of populations change in response to environmental conditions
Size – number of individuals
Density – number of individuals in a certain space
Distribution – spatial pattern – clumping,uniform dispersion,
random dispersion
Age distribution structure - percentage of individuals in each age group
uniform
Clumping
random

6. What limits population growth?
Birth, death, immigration, emigration

7. Population change = (birth+ immigration) - (death + emigration)
dependent on resource availability or other environmental changes

8. Intrinsic rate of increase®
rate at which a population could grow if it has unlimited resources
always limits - light, water, space, nutrients
“High r” – reproduce early in life, short generation ie. reproduce many times many offspring: house fly

9. Carrying capacity - capacity for growth
number of individuals of a given species that can be sustained indefinitely in a given area (K)
determined by interaction between biotic potential and environmental resistance (factors that act jointly to limit a population)

10. Population Dynamics and Carrying Capacity
Basic Concept: Over a long period of time, populations of species in an ecosystem are usually in a state of equilibrium (balance between births and deaths)
There is a dynamic balance between biotic potential and environmental resistance

11. Carrying Capacity (K)
Exponential curve is not realistic due to carrying capacity of area
Carrying capacity is maximum number of individuals a habitat can support over a given period of time due to environmental resistance (sustainability)

15. Biotic Potential
Ability of populations of a given species to increase in size
Abiotic Contributing Factors:
Favorable light
Favorable Temperatures
Favorable chemical environment - nutrients
Biotic Contributing Factors:
Reproductive rate
Generalized niche
Ability to migrate or disperse
Adequate defense mechanisms
Ability to cope with adverse conditions

16. Environmental Resistance
Ability of populations of a given species to increase in size
Abiotic Contributing Factors:
Unfavorable light
Unfavorable Temperatures
Unfavorable chemical environment - nutrients
Biotic Contributing Factors:
Low reproductive rate
Specialized niche
Inability to migrate or disperse
Inadequate defense mechanisms
Inability to cope with adverse conditions

18. Population Density
Population Density (or ecological population density) is the amount of individuals in a population per unit habitat area
Some species exist in high densities - Mice
Some species exist in low densities - Mountain lions
Density depends upon
social/population structure
mating relationships
time of year

19. Reproductive Strategies
Goal of every species is to produce as many offspring as possible
Each individual has a limited amount of energy to put towards life and reproduction
This leads to a trade-off of long life or high reproductive rate
Natural Selection has lead to two strategies for species: r - strategists and K - strategists

20. r - Strategists Spend most of their time in exponential growth
Maximize reproductive life
Minimum life K

21. R Strategists Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental conditions
High population growth rate – (r)
Population size fluctuates wildly above and below carrying capacity – (K)
Generalist niche
Low ability to compete
Early successional species

22. K - Strategists Maintain population at carrying capacity (K)
Maximize lifespan K

23. K- Strategist Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental conditions
Lower population growth rate (r)
Population size fairly stable and usually close to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species

24. Survivorship Curves
Late Loss: K-strategists that produce few young and care for them until they reach reproductive age thus reducing juvenile mortality
Constant Loss: typically intermediate reproductive strategies with fairly constant mortality throughout all age classes
Early Loss: r-strategists with many offspring, high infant mortality and high survivorship once a certain size and age

25. Survivorship curves
proportion of survivors of a particular species in a particular age group
a)late loss – type I - elephant
b) early loss – type II songbirds
c) constant loss - intermediate reproductive strategies- starfish

26. Population growth
J-shaped - exponential growth curve, growth starts slowly then speeds up
S - shaped curve- logistic growth curve - slow start, rapid exponential growth, levels off when K is reached

27. Population cycles in nature
relatively stable - slight fluctuation above and below carrying capacity, tropical rain forest
erupt - high peak, crash - raccoons
cyclic - “boom” and “bust”

28. Effect of population density on population growth?
Density Independent – floods, drought, hurricane, habitat destruction, pesticide spraying
Density dependent – competition for resources, predation, disease – infectious diseases – plague in Europe

29. Communities and ecosystems respond to environmental change
Primary succession- gradual establishment of biotic communities in life less areas where there is no soil in a terrestrial ecosystem or nobottom sediment in an aquatic ecosystem
Secondary succession –series of comunities or ecosystems with different species develop in places containing soil or bottom sediment

30. Primary succession
bare rock subject to weathering crumbles into particles, releasing nutrients
Pioneer or early successional species (lichens or mosses)attach to rock and start the process of rock formation by secreting mild acids
Mid successional plants – grasses, herbs, small plants
Late successional species trees that can tolerate shade

31. Secondary succession
ecosystem has been disturbed , removed or destroyed, some soil or bottom sediment remains
abandoned farmland, burned or cut forests,heavily polluted streams, flooded lands

32. Living systems are sustained through constant change
complex system of positive and negative feedback loops that interact to provide stability
Inertia or persistence – ability of a living system such as grassland or forest to survive moderate disturbances
Resilence – ability of a living system to be restored through secondary succession after a moderate disturbance

33. Conservation Biology Investigate human impacts on biodiversity
Develop practical approaches to maintaining biodiversity
endangered species management, wildlife reserves, ecological restoration, environmental ethics

34. Prevent premature extinction how ?
Status of natural populations, species in danger of extinction
Status of the functioning of ecosystems
Measures taken to maintain habitat quality which will support wild species population

35. Understand status of natural populations
Measure current population size
Determine how size will change with time
Determine whether populations are sustainable

36. Anthropogenic impact
Fragmenting or degrading habitat, simplifying natural ecosystems, strengthening genetic resistance to pesticides, eliminating predators, introduce alien species, over harvesting, interfering with nutrient cycles

37. Working with Nature Learn six features of living systems
Interdependence
Diversity
Resilience
Adaptability
Unpredictability
Limits

38. Basic Ecological Lessons
Sunlight is primary source of energy
Nutrients are replenished and wastes are disposed of by recycling materials
Soil, water, air, plants and animals are renewed through natural processes
Energy is always required to produce or maintain an energy flow or to recycle chemicals

39. Basic Ecological Lessons
Biodiversity takes many forms because it has evolved over billions of years under different conditions
Complex networks of + and – feedback loops exist
Population size and growth rate are controlled by interactions with other species and with abiotic
Organisms generally only use what they need

40. Four Principles for Sustainable
We are part of, not apart from, the earth’s dynamic web of life.
Our lives, lifestyles, and economies are totally dependent on the sun and the earth.
We can never do merely one thing (first law of human ecology – Garret Hardin).
Everything is connected to everything else; we are all in it together.