The Living World Continued: Populations and Communities
Ecosystem Communities Populations
Review: Parts of an Ecosystem 1) An individual in a species: One organism of a species. a species must be genetically distinct and have the ability to reproduce with another of that species. 2) A population: a group of individuals of the same species, living in a shared space at a specific time.
3) A community : All the different populations in an ecosystem. To be a community there must be 2 or more populations living and interacting in the same ecosystem. ex. alpine ecosystem sheep, mice, goats and insects (animal populations) 4) A habitat: The place in which an organism lives. A habitat provides the kind of food, shelter, temperature, and amount of moisture the organism needs to survive.
Review: Ecosystems Ecosystems are a community of living organisms interacting with one another and with the non-living components of the environment they inhabit. It refers to all the living organisms (biotic elements) along with the nonliving features (abiotic elements) of their environment.
Population Size Population Size: refers to the number of individuals in a population. Population size is very fluid; it can increase, decrease or remain stable over time. 4 factors affect population size: 1. Births 2. Deaths 3. Immigration: the arrival of individuals from other regions 4. Emigration: departure of individual to other regions
Factors increasing the size of a population Births & Immigration Factors decreasing the size of a population Deaths & Emigration
Ecological Factors that Affect Population Size An ecological factor is an aspect of a habitat that can affect the population size of the organisms living there. Three types of ecological factors: 1. Abiotic (non-living) factors: ecological factors of physical or chemical origin. 2. Biotic (living) factors: ecological factors related to the actions of living organism. 3. Limiting factor: a strong (abiotic or biotic) factor that causes the density of a population to decrease.
Ecological Factors The absence or presence of ecological factors can change the density of a population in a habitat. Abiotic Biotic Amount of light Birth rate Soil or water ph Disease Terrain Predation Depth of snow Amount of food Temperature Competition Air humidity Human activity
Population Density Population density is the number of individuals per unit of area. Population Density = Number of individuals Space occupied Population density can be dependent on: access to food and water climate interactions with other populations disturbances to the habitat
Example #1 Question: In 1970, the estimated population of grasshoppers is 1434 on a 22 acre farm. What is the population density of grasshoppers? Population Density = Number of individuals Space occupied
Example #2 Question: On day one, there are 30 rabbits in 50 m2 Happy Field. The next day, there are 60 rabbits. On day three there are 100 more rabbits. What is the population density of rabbits in Happy Field on day 1, day 2 and day 3? Population Density = Number of individuals Space occupied Answer: Day One: = Day Two: = Day Three: =
Example #3 Question: Atlantis is a city under the ocean with an are of 150,000 m2. In 2016, there was 3345 people living there. In 2017, there were 300 births and 22 deaths. What is the population density of Atlantis at the end of 2017? Answer: 1) Number of individuals: 2) Space Occupied = 150,000Density m2 Population = Number of individuals Space occupied 3)
What do you notice about the populations on this map?
Population Distribution Population distribution is how the individuals in a population are spread out within their habitat. There are 3 main patterns of population distributions:
Clumped Distribution Clumped distributions are when the individuals form groups or clusters. Most common pattern. Often observed in areas of the habitat with better living conditions (food and protection).
Uniform Distribution Uniform distributions are when the individuals are scattered equally throughout the population s habitat. Often due to competition for resources (food and shelter).
Random Distribution Random distributions are where the individuals are scattered without any pattern or predictability. Rarely found in nature.
What is the distribution of this tree population? Uniform distribution
1. What is the distribution of the red fish population? Clumped distribution 2. What is the distribution of the blue fish population? Clumped distribution 3. What is the distribution of the white fish population? Random distribution
What is the distribution of this artichoke plant population? Uniform distribution
What is the distribution of this elephant population? Clumped distribution
Question #1: Carrots planted by a farmer are all lined up in a row. This is an example of which type of distribution? a) Clumped distribution b) Random distribution c) Uniform distribution Answer: c) Uniform distribution
Question #2: Orca whales travel in families throughout their entire lives. As a result, they are rarely found alone in nature. This is an example of what type of distribution? a) Clumped distribution b) Random distribution c) Uniform distribution Answer: a) Clumped distribution
Community Interactions Recall, a community is a set of populations of different species sharing the same habitat. Interactions between species in the same community include: 1. Competition 2. Predation 3. Parasitism 4. Mutualism 5. Commensalism Fig. 8: http://www.ebay.com/itm/11-x14-art-print-for-kids-jungle-safarianimals-/260337134835
Competition Competition: the interaction between living organisms that seek access to the same resource in their habitat. There are 2 types of competition: 1. Intraspecific: Competition between individuals of the same species. 2. Interspecific: Competition between individuals of different species.
Predation Predation: the interaction between two living organisms in which one feeds on the other o Predator: individual that feeds on the other o Prey: the individual being eaten Example: Predator = ladybug Prey = Green bug
Parasitism Parasitism is a form of predation in which one species draws its food by living inside or on the surface of the other o Parasites are individuals that gain something from their host. o Hosts are individuals who are harmed in some way because of the parasite. Example: Parasite = mosquito Host = human
Mutualism Mutualism is the interaction between two living organisms that benefits both organisms Example: The clown fish (Nemo) lives inside the poisonous anemone for protection from predators, while the clown fish lures other fish towards the anemone for it to prey on.
Commensalism Commensalism is the interaction between two living organisms in which one organism benefits from the relationship while the other remains unaffected Example: The bird gets to build it s nest in the tree, while the tree remains unaffected by the nest s presence
Biological Cycle Biological cycles are alternating periods of rise and fall of the size of a population. These periods are of fixed duration and are repeated continually.
During predation, the prey population usually needs to increase for the predator population to increase. Why? Due to the fact that the predators feed off of the prey population, the two populations are linked.
Example #1 The graph below represents what type of community interactions? How do you know? As one species population declines to zero, the other population continues to increase this indicates competition.
Example #2 The graph below represents what type of community interactions? How do you know? When organism 2 lives with organism 1, organism 2 benefits greatly and increases, while organism 1 remains unaffected This indicates commensalism.
Biodiversity Biodiversity describes the variety of species living in a community. How is biodiversity measured? 1. Number of species in the community (Species Richness) 2. Relative abundance of each species Biodiversity is high when: 1. The number of species is high 2. The relative abundance of different species is similar (similar percentages)
Number of Species Count the number of species in Habitat A. The more different types of species, the more species rich the ecosystem is. The number of species in the image is 5.
Number of Species How many species are there in this picture? A) B) C) D) 20 species 19 species 5 species 6 species B Answer: c) 5 species Fig. 17: http://www.landlearn.net.au/print/habitat.ht m
Relative Abundance Relative Abundance = Species A: 4/ 20 = 20% Species B: 4/ 20 = 20% Species C: 4/ 20 = 20% Species D: 4/ 20 = 20% Species E: 4/ 20 = 20% C A B E D
Exit Card 1. 2. On a sheet of paper, to hand in at the end of class answer the following 2 questions: What is the relative abundance of the different fish species in Habitat B? Compare Habitat A and B. Which habitat has the greatest biodiversity? Explain your answer. B C D E A
Relative Abundance Calculate the relative abundance in Habitat B: A B C D E i) 1 1 1 1 15 Total 19 19 19 19 19 iii) 5.25 % 5.25 % 5.25 % 5.25 % 78.9% B C D E A
Compare Habitat A and B. Which has the greatest biodiversity? Explain your answer. Habitat A has the greatest biodiversity. Both habitats have the same number of species but in habitat A the relative abundance of each species is the same whereas in Habitat B, species E is clearly the most abundant.