Factors affecting population growth ● Density dependent factors ○ intraspecific + interspecific competition ■ intraspecific : stress in limited resource ● Between same species ● Used for population regulation ■ Interspecific: ○ Crowding different species compete on limited resources ■ Cross species interaction ■ Resource limited ■ Often harm more than one species (competitive exclusion) ○ Parasitism ○ Disease ○ Predation ● Fecundity ○ Reproductive age ○ Offspring per reproductive phase ○ Number of cycle of reproduction per lifetime ● Density independent factors ○ Temperature ○ Disturbance ○ Quality of food ● Generational time ○ Average time between generations ■ Bacteria (E.coli) 20min ■ Chichen 6 months ■ Humans 20-30 years Impact of humans ● Conservation ○ Facilitating reproduction to conserve ● Biological Control ○ Introduction of new species ○ Used to control other species ● Introduction of Exotic Species ○ Invasive species are introduced to the environment ● Habitat changes ○ Alteraltion ● Climate change ● Hunting(fishing) ● Agriculture Trophic Roles ● Species exists as part of a system ● One organism may have multiple roles in the system ● Trophic Cascade ○ Removing one species from the system might impact the whole system ● Producers are mostly photosynthesizer ● Eagle could have multiple roles ○ When eagle eats grass, it would both be tertiary and primary consumers ● Due to complicated relationship, may have wide spread effects ○ Does not only impact organism linked directly but also other organisms linked in the system ● Trophic role ○ Decomposers ○ Primary producers ○ Primary consumers … Interspecific Interactions ● Interspecific interaction ○ Predator-prey ■ One eats another ■ Herbivory ● Plant eaters eating primary producers ○ Competition ■ Two species fighting over single resources ■ Resource usually limited ● Symbiosis ○ Commensalism ■ One species benefits, other neutral ○ Mutualism ■ Both species benefits ○ Parasitism ■ One species benefits, other take harm ex) Human in mutualism with microorganisms in our systems