A group of organisms that can interbreed and produce fertile offspring Species A group of organisms that can interbreed and produce fertile offspring Common gene pool Have similar physiological/morphological characteristics Are genetically distinct from other species Have common phylogeny (family tree) Challenges: What about two populations that could potentially interbreed, but do not because they are living in different niches or are separated by a long distance? How should we classify populations that do not interbreed because they reproduce asexually? What about infertile individuals? Does the fact that a couple cannot have a child exclude them from the species? What about in vitro fertilization?

Challenges to species definition Hybrids Two separate species produce offspring  not fertile Due to different number of chromosomes Not considered distinct species – cannot create future generations Horse: 64 (32) Donkey: 62 (31) Lion: 38 (19) Tiger: 38 (19) Genetic barrier Horse: 64 (32) Zebra: 32-46 (16-23)

Reproductive Isolation Group of species separated from rest Geographic Isolation: Bodies of water, mountains, continent moving, forests Separate species  only able to reproduce with its population  traits may start to vary Behavioral isolation: Migration patterns change – change nesting times Courtship patterns change – changing whose attracted to whom

Communities Ecosystems Group of populations living and interacting with each other in an area Interactions of biotic and abiotic factors Abiotic measurements allows for predictions on type of species living in that ecosystem Feeding relationships, symbiotic relationships, protection, parasitic Studied via random sampling or systematic sampling

Autotrophs Make own organic molecules from inorganic molecules Producers

Heterotrophs Must obtain organic molecules from other organisms Consumers Consumers ingest energy rich C-compounds, proteins, lipids to grow, repair, operate Saprotrophs Detritivores Live in/on non-living organic matter Eat non-living organic matter Breakdown nutrients via external digestion Breakdown nutrients via internal digestion humus

Saprotrophs Role Nutrient Cycling Finite amount of nutrients – must be recycled Role = breakdown waste material Secrete enzymes into dead tissue Break down complex molecules into simpler energy-rich compounds Saprotrophs/organisms absorb products Create rich soil that is needed to sustain life

Sustainability