Some seeds are hard outside so they pass through the birds' guts and are dropped on the ground...
One of the characteristics of the seeds or fruits is that it usually has a hard shell and is hollow inside.
Some fruits, such as peaches, mangoes and avocados contain just one large seed inside a hard stone. Other fruits, such as Oranges, lemons, apples, and Pears, contain several seeds called pips. Berries have lots of tiny pips around the outside of each fruit.
Pine cones have seeds inside their scales. The seeds are located at the base of each scale and are dispersed when the cone opens or breaks apart.
A good rule of thumb is, if the seed is hard, don't eat it. You would naturally eat cucumber, pea, bean and tomato seeds, but not apple or peach seeds. Melon, sunflower and squash seeds are edible even though you might find them hard in the fruit, but they are exceptions to the rule.
Yes, some seeds have hard outer shells and sticky interiors when cracked open. A notable example is the seed of the tamarind fruit, which has a tough, brown pod that encases sweet and sticky pulp. Similarly, the seeds of the longan fruit are hard on the outside while the flesh inside is gelatinous and sweet. These characteristics help protect the seeds while providing a nutritious reward for animals that help in their dispersal.
Some fruits, such as peaches, mangoes and avocados contain just one large seed inside a hard stone. Other fruits, such as oranges, lemons, apples, and pears, contain several seeds called pips. Berries have lots of tiny pips around the outside of each fruit.
The Ethelyn gas is produced by the fruits. If you keep your fruits in the refrigerator the Ethelyn gas will stay inside the fruit and will not be able to come out because it is hard for it yo expand so if you keep your fruits outside the refrigerator then your fruits will last longer.
That is just like asking why are we hard on the outside and all gushy and bloody on the inside
Almonds and walnuts are classified as nuts, not as fruits. While fruit has the evolutionary function of serving as food for animals that eat the fruit and spread the seeds contained in the fruit, nuts do not have that purpose. They have shells to protect them from being eaten, so that their nutritional content can instead by used to feed a new plant that can grow from the nut.
ambot
Inside apples. They are the hard, dark bits.
Biologically speaking, all 'fruits' have seeds, as that is the definition of a fruit. The fruits we see for sale at grocers and supermarkets however, have been specially bred for human consumption - namely more edible flesh, and a lack of seeds. They are very different from how they appear in the wild - a natural banana is packed with hard seeds for example.