Reproduction - Double Fertilization

Ecology And Environment - Population Intractions

Mutualism : Both the interacting species are benefited.

Ex.
1. Lichens = Fungi + Algae
2. Mycorrhizae = fungi + Roots of higher plants
3. Ophrys :

Ophrys is a large group of orchids from the alliance Orchis in the subtribe Orchidinae. These plants are remarkable in that they successfully reproduce through pseudocopulation, that is, their flowers mimic female insects to such a degree that amorous males are fooled into mating with the flowers, thereby pollinating them.
They are referred to as the "Bee orchids" due to the flowers of some species resemblance to the furry bodies of bees and other insects. 
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Predation : In ecology, predation describes a biological interaction where a predator (an organism that is hunting) feeds on its prey .

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Parasitism : Parasitism is a non-mutual relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host.

Ex. Brood parasitism : Is the phenomenon in which one parasitic bird species lays its eggs in the nest of another bird species.

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Commensalism : Is an interaction in which one species is benefited while the other species is neither benefited nor harmed.
Ex. Orchids grow as epiphytes on mango trees or other fruit trees. (orchids are benefited by getting shelter,while the tree is neither benefited nor harm.

Ex. 

Cattle egrets and livestock

An example of commensalism: cattle egrets foraging in fields among cattle or other livestock. As cattle, horses and other livestock graze on the field, they cause movements that stir up various insects. As the insects are stirred up, the cattle egrets following the livestock catch and feed upon them. The egrets benefit from this relationship because the livestock have helped them find their meals, while the livestock are typically unaffected by it.

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Competition : Harmfull for both.

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Amensalism : One is harmed and other is neither harmed nor benefited.

Ex. The black walnut secretes a chemical from its roots that harms neighboring plants, an example of amensalism.

Reproduction - Fertilization and cleavage

In embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula.