UNIT 1: LESSON 3 AND 4 Lesson 3: Population dynamics Lesson 4: Interactions in Communities

MOVIN’ OUT By Immigration and Emigration Populations can grow bigger or get smaller. Immigration – when individuals join a population. Into a new population. Population gets larger. Emigration – when individuals leave a population. Exiting a population. Population gets smaller.

MOVIN’ OUT By Birth and Death Birth = increase in population. Death = decrease in population. The number of births compared to the number of deaths tells if a population is increasing or decreasing.

MOVIN’ OUT Births Deaths Population Immigration Emigration

KNOW YOUR LIMITS Resource Availability Each environment has different amounts of resources that living things need, such as food, water and space. Resources influence population size. If resources decrease then population size will decrease. If resources increase then population size will increase.

KNOW YOUR LIMITS Resource Availability Carrying Capacity – the maximum number of individuals of one species that the environment can support. Carrying capacity changes when the environment changes. Population crash = carrying capacity drops Examples include: natural disasters like forest fires, harsh weather, drought, etc. Population growth = favorable environmental conditions. New food growth, great weather, etc.

MAXIMUM CAPACITY Limiting Population Size Limiting Factor – a part of the environment that keeps a population’s size at a level below its full potential. They can be living or nonliving things. Abiotic Factor – nonliving parts that are needed for survival. Water, nutrients, soil, sunlight, temperature, living space. Biotic Factor – living organisms interacting.

ORGANISM INTERACTIONS Sometimes interactions can help one individual, harm another or help both. Competition – when 2 or more individuals or populations try to use the same limited resources such as food, water, shelter, space, sunlight, etc.

ORGANISM INTERACTIONS Cooperation – occurs when individuals work together. It helps individuals get resources, which can make populations grow. Example: hunting in groups, stay close together for warmth, structured social order in bees and ants.

PREDATOR vs PREY Feeding Relationships Predator – eats another animal. Prey – an animal that is eaten. An animal can be both predator and prey!

PREDATOR vs PREY Feeding Relationships Animals have adaptations that help aid in survival. Examples include: talons, claws, sharp teeth, webs, camouflage, defense chemicals.

Camouflage

PREDATOR vs PREY If a prey population grows or shrinks, the number of predators the community can support changes as well.

SYMBIOTIC REALTIONSHIPS Living Together Symbiosis – a close long-term relationship between different species in a community. They might benefit, be harmed or remain unaffected. 3 types 1. Mutualism – Both organisms benefit.

SYMBIOTIC REALTIONSHIPS Living Together 2. Commensalism – one benefits and the other is unaffected. 3. Parasitism – One benefits and the other is harmed. Parasite = benefits Host = one harmed