Chapter 13 Populations and sustainability By the end of this session I should be able to: (a) explain the significance of limiting factors in determining the final size of a population; (b) explain the meaning of the term carrying capacity; (c) describe predator–prey relationships and their possible effects on the population sizes of both the predator and the prey; (d) explain, with examples, the terms interspecific and intraspecific competition; (e) distinguish between the terms conservation and preservation (HSW6a, 6b);

Bacterial Growth Curve In a closed system, the organisms will eventually produce toxic by-products and die because the carrying capacity of the growth medium has been exceeded. http://pathmicro.med.sc.edu/fox/growth_c.jpg

World Population Density, 2000 The Global Education Project

World Population Density – Another View National Geographic Atlas of the World, Eighth Edition

In reality what does the carrying capacity look like?

Carrying Capacity The population that an area will support without undergoing environmental deterioration. The carrying capacity of an environment tends to limit population size. Food availability, reproductive behaviour, and infectious diseases tend to keep animal (and human) populations in check.

Abiotic factors are the non-living Components of the Environment Abiotic factors include: Sunlight Water Temperature Wind Soil/substrate Special events such as: Fires Hurricanes Floods Volcanic eruptions Tsunamis

Biotic Factors  A living organism is also affected by the living components of its environment. Predators feed on members of the population. Microbes can bring diseases. (If time travel were possible, and you could be transported to the Cretaceous Era to look at dinosaurs, don’t be afraid of fear Tyrannosaurus, fear the microbes. You would have no immunity to them!!) There may be competition for nesting space. Plants may compete for the light needed to carryout photosynthesis. These are many other biological factors determine the success of an individual or species. Competition exists for available food resources.

Predator – Prey Relationships: A Description (Madler, 1998) The predator’s abundance curve almost always lags behind that of the prey. WHY?? (2 marks)

In reality the pattern is not always followed In reality the pattern is not always followed!! Circle areas on the graph where the is the case.

Discussion pairs – 2 minutes Suggest reasons for the areas that you have circled on the graph where the typical predator prey pattern is not followed. (3 marks)

Competition key terms  4 Minutes Definition Plant eg Animal eg Compete Intraspecific Competition Interspecific Niche

Describe and explain the trend on the graph below. (5 marks)

Conservation Vs Preservation Key Term Definition Describe an example Conservation Preservation Biodiversity Niche