Answer :
Hybrid sterility: Hybrids are born but cannot reproduce. Example: Mules.
Mechanical isolation: Reproductive parts don't fit together. Example: Incompatible insect genitalia.
Gametic isolation: Sperm and egg cannot fuse. Example: Sea urchin sperm and egg incompatibility.
Temporal isolation: Species breed at different times. Example: Spring vs. fall flowering plants.
Geographical isolation: Populations are physically separated. Example: Squirrels on opposite sides of a canyon.
What connects them? They are all types of reproductive isolation, preventing different species from interbreeding.