Chapter 8 Characteristics of Populations Population Dynamics Chapter 8 Characteristics of Populations

Key Questions Heinemann Biology 1 Relationships in an Ecosystem 7.2 Review Questions 1-6

Revisual

Revisual

Revisual

Keystone Species Keystone species maintain the structure of its ecosystem. e.g. top predators

Keystone Species Loss or removal of a keystone species results in less stable ecosystems and structural changes.

Sea Star Population - Keystone Predator: Sea Star Ecosystem: Rock pool Experimental group Increased mussel population Decreased algal population

Great White is a Keystone sp. too!

Word Work! Population dynamics: The study of change in population size over time. Population: A number of organisms of the same species that live in a defined geographic area. Abundance: The size of the population. Density: The number of individuals per unit area or volume. Distribution: Where a species lives: it’s geographic range and its preferred habitat

What do you think? Can you estimate the current world population? http://www.worldometers.info

Population Characteristics Population Size

Population Size Population size is determined by four primary events: Birth Death Immigration Emigration

30 – 15 = + 15 (population increase of 15) Mathematically… Change in population size = (births + immigration) − (deaths + emigration) ENTRIES – EXITS e.g. (20 B + 10 I) – (5 D + 10 E) = 30 – 15 = + 15 (population increase of 15)

Pause and Think Which of the following describes a population that is increasing in size? (B= birth, D= death, I= immigration, E= emigration) (B + D) > (I + E) (B + E) > (D + I) (D + E) < (B + I) (B + E) < (D + I)

Population Characteristics Population Density

Word Work! Density

Word Work! The density of bone tissue decreases in osteoporosis sufferers.

Abundance (or density) Can be expressed: qualitatively, e.g. scarce or rare, infrequent, frequent, abundant, very abundant quantitatively, e.g. the number of ants per square metre.

Pause and Think One study identified 54 Tasmanian devils living in an area of 80 square kilometres in Tasmania. What will be the abundance of this population, in quantitative terms (abundance/km2)? 54/80 = 0.675 = ~ 0.7 animals/km2

Population Characteristics Population Distribution Occupation of a population with respect to one another. Random Uniform Clumped

Pause and Think Identify the type of distribution (random, uniform or clumped) observed in each population below. Clumped Uniform Random

Pause and Think CLUMPED

Pause and Think UNIFORM

Pause and Think RANDOM

Pause and Think If some cattle wandered off, would they still be considered part of the population? If a new herd came by, would they be part of the existing population?

Factors that determine Distribution and Abundance 1. Characteristics of environment – Abiotic factors 2. Characteristics of the organism (adaptations) – particular features allow an organism to survive and reproduce 3. Interactions between organisms – including availability of prey, parasites, competition

Key Questions 1. Label the blanks in the diagram with the four processes that affect population size. Population Size Increase Decrease

Key Questions 2. State whether each factor is a biotic or abiotic factor. Water Trees Algae Animals pH Salinity Soil Hawk

Key Questions 3. Use a specific example to explain how one abiotic factor can affect population growth. 4. a) Compare interspecific and intraspecific competition and give an example of each. b) Name three limiting factors that affect population growth.

Biozone 139 – The Role of Keystone Species 140 – Population Density and Distribution 141 – Measuring Distribution and Abundance