May 9, 2018 Journal: Draw a food chain with four organisms.

Population Growth

Niches A. A good habitat must provide: 1) Food 2) Water 3) Shelter 4) Space B. Within its habitat, each organism has a niche – the role that it plays 1) No two organisms can occupy the same niche

Examples of Niches A. Fungus – decays dead matter and returns needed nutrients to the soil B. Plants – begin the food chain; provide shelter for many animals; supply oxygen C. Predators – occupy top trophic levels; eliminate weak/old prey

Population Characteristics Population Density: The number of organisms in an area Spatial Distribution: The pattern of spacing in a population within an area caused by availability of resources Three types of dispersion Clumped Uniform Random

Population Limiting Factors 1. Population growth rate: how fast a given population grows Factors that influence this are: - Birthrate - Death rate - Emigration - the number of individuals moving away from a population - Immigration - the number of individuals moving into a population

Population Limiting Factors 2. Density-independent factors: factors that limit population size, regardless of population density These are usually abiotic factors They include natural phenomena Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

Population Limiting Factors Density-dependent factors Any factor in the environment that depends on the number of members in a population Usually biotic factors These include Predation Disease Parasites Competition

So, what do you think is going to happen to the human population?

Exponential Growth Model Exponential growth model – Population size continuously grows Also called J-shaped growth.

Limits to Exponential Growth Population Density increases as well which leads to increased competition When a population size reaches the maximum level that a particular environment can support it is said to have reached carrying capacity 11

Logistic Growth Model Often called the S-shaped growth curve Occurs when a population’s growth slows or stops following exponential growth once the population reaches carrying capacity 12

May 2017 Journal:

Communities A community is a group of interacting populations that occupy the same area at the same time.

Range of Tolerance The limits within which an organism can exist

Ecological Succession The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

Ecological Succession Community Ecology: Ecological Succession Ecological Succession Ecological Succession Consists of 2 types: Primary Succession Secondary Succession

Primary Succession The establishment of a community in an area of exposed rock that does not have topsoil It occurs very slowly at first Lichens or mosses are first organisms to arrive They secrete acids that can break down rock Their dead, decaying organic materials, along with bits of sediment from the rock make up soil. Then small plants move in, followed by larger plants and animals

Secondary Succession Disturbances (fire, flood, windstorms) can disrupt a community, which allows new species to occupy the habitat afterwards. Organisms that move in are usually those that surround the site of the disturbance Occurs faster than primary succession

Biodiversity - The variety of life in an area that is determined by the number of different species in that area. - Increased biodiversity is a sign of a more stable community

Extinction Rates The gradual process of becoming extinct is known as background extinction. Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time. 250 MYA: Over 90% of species died

Estimated number of Extinctions since 1600 Biodiversity and Conservation: Extinctions Estimated number of Extinctions since 1600 Group Main-land Island Ocean Total Approximate Number of Species Percent of Group Extinct Mammals 30 51 4 85 4000 2.1 Birds 21 92 113 9000 1.3 Reptiles 1 20 6300 0.3 Amphibians 2 4200 0.05 Fish 22 23 19,100 0.1 Invertebrates 49 48 98 1,000,000+ 0.01 Flowering Plants 245 139 384 250,000 0.2 Since the mid-1970s there has been an alarming decrease of amphibian populations, and many are on the verge of extinction.

Five Most Recent Mass Extinctions Cretaceous Period (65 MYA) Triassic Period (200 MYA) Permian Period (250 MYA) Devonian Period (360 MYA) Ordovician Period (444 MYA)