50/50 - Flower ovary

In flowering plants the ovary is a part of the female reproductive organ and is the part of the pistil that holds the ovules. Above the ovary is the style and the stigma where the pollen lands and germinates for each individual pollen grain to fertilize an ovule.

49/50 - Dominant vs. recessive phenotype

Phenotypes are the physical characteristics of an organism. Dominant alleles are usually more common than recessive alleles. This is mainly because a recessive trait needs two under case letters to be present while a dominant trait needs only one upper case letter to be present. For example, unattached ear lobes are a dominant trait while attached ear lobes are recessive.

48/50 - Tropism

A tropism growth or turning movement of an organism like a plant in response to its environment. This response is dependent on the direction of the stimulus and may be either positive (towards the stimulus) or negative (away from the stimulus).

47/50 - Succesion

Succesion is the series of changes in a community that happen over time. The community usually begins with relatively few plants and animals and develops until it becomes stable enough to be called a climax community.

46/50 - Stigma & style of carpel

The stigma is the receptive tip of a carpel and receives pollen during pollination. It adapted to catch and trap pollen with various hairs and flaps. The pollen may also be captured from the air, water or visiting insects. The style connects the stigma to the ovary and pollen tubes grow to the length of the style to reach the ovules.

45/50 - Rhizome

A rhizome is a modified stem of a plant that is usually found underground and sends out roots and shoots from its nodes. They develop from buds and grow vertical to the force of gravity. The rhizome also has the ability to grow new shoots upward. In this picture, you can see some of the roots of the tree  sticking out of the ground.

44/50 - Population

A population is a group of all the organisms of the same species who live in the same area and are capable of interbreeding. The probability of interbreeding is higher than the probability of cross-breeding with organisms from other areas and breeding is more common within the area then outside of it.

43/50 - Pollen

Pollen is a powder containing gametophytes of seed plants that produce the male sperm cells. When pollen lands on a compatible female cone like when pollination occurs it germinates and transfers the sperm to the ovule.

42/50 - Niche

Organisms have niches so that they can survive better and if every organism is doing the same thing then it would be difficult to survive because of competition. Every organism has a niche, it's how they have food and shelter and it's also how they either directly or indirectly play their role in the ecosystem.

41/50 - Mutualism

Mutualism is the way two organisms of different species benefit each other.  Mutualism is different from exploitation or parasitism where one species benefits at the expense of the other. Mutualism is a type of symbiosis where both organisms gain an advantage from their relationship.

40/50 - Modified stem of a plant

Modified stems of a plant elevate the leaves and serve as a channel from the roots to the leaves and generate new growth. Stolons like a cactus are oriented horizontally and are adapted to create new plants that are identical to the original.

39/50 - Modified root of a plant

Modified roots of a plant are adapted to their environment allowing them to do things like secure energy and other resources. Some modified roots are able to keep the plant secure and absorb water and mineral nutrients. A modified vine may form roots that help the plant bond to a substrate.

38/50 - Modified leaf of a plant

A modified leaf is a leaf that is changed for a certain purpose and some functions it can perform are transpiration and photosynthesis. An example of this would be that stipules can adapt and form spines for defense.

37/50 - Homologous structures

Homologous structures don't always have the same function but they come from the same common ancestor. For example, a bone that exists inside the ear of mammals is a homologous structure to some species of fish.

36/50 - Eubacteria

Eubacteria is complex and single celled and most bacteria are in the eubacteria kingdom. Eubacteria is classified in its own kingdom because their chemical makeup is different. Most eubacteria are helpful and some produce vitamins and foods like yogurt but some eubacteria can give you strep throat.