Savvas Realize Topic 4

Asexual Reproduction

• Asexual reproduction is a reproductive process that involves only one parent and produces offspring that are genetically identical to the parent. In fragmentation, a new organism forms from a piece of the original (ex: starfish). In budding, a new animal grows out from the parent until it fully matures and breaks off (ex: sponges).

Sexual Reproduction

• In sexual reproduction, two parents combine their genetic material to produce a new organism that differs from the parents. It involves a sperm cell (father) and egg cell (mother) joining to form a new cell in a process called fertilization. Each parent gives half their chromosomes so the offspring has a full set.

Traits and Genes

• A specific characteristic that an organism passes to its offspring through its genes is called a trait. A gene is a sequence of DNA that determines a trait passed from parent to offspring. Differences in offspring are known as variations.

Comparing Types of Reproduction

• Benefits of asexual reproduction are that organisms don't need to find a mate, and can reproduce quickly. However, all offspring have exactly the same genetic makeup, which can be a problem if the environment changes. Benefits of sexual reproduction are that offspring have more genetic variation (increasing their chances of survival if the environment changes). However, the organism needs to find a mate.

Inherited Traits

• Inheritance is the process in which offspring receive traits from their parents. Genes are located on chromosomes and describe the factors that control a trait. Each trait has a gene from the mother, and a gene from the father (which can be the same or different).

Alleles

• An allele is a different form of the same gene. One allele is received from each parent and the combination of alleles determines the offspring's traits. If an offspring inherits a dominant allele from either parent, that trait will always show up. An offspring has to receive two recessive alleles from both parents for the trait to show up.

Incomplete Dominance & Codominance

• Sometimes, intermediate forms of a dominant trait appear. This creates a mixture/blending of the recessive and dominant traits known as incomplete dominance (ex: pink rose). Codominance is when two alleles are expressed. (ex: spotted flowers, AB blood)

Multiple Alleles

• Some traits have multiple alleles, such as blood type (A + B are codominant, O is recessive).

Polygenic Inheritance

• In polygenic inheritance, different genes are expressed to produce a trait (ex: human height, skin color; there is a range).

Acquired Traits

• Traits that are learned are called acquired traits. The combination of inherited and acquired traits helps an organism to survive

Environmental Traits

• The environment can lead to changes in gene expression. (ex: chemicals in tobacco or exposure to the sun's UV rays) IN order to pass on genes that have been affected by the environment, the change must occur in the sperm or egg cells.

Plant Life Cycles

• Plants have two different stages of their life cycle: the sporophyte stage and the gametophyte stage. In the sporophyte stage, a plant produces spores that develop into gametophytes. In the gametophyte stage, male and female sex cells are produced, which are needed for fertilization.

Nonvascular Plants

• Nonvascular plants (plants that absorb nutrients and water through their surface; moss) produce sporophytes that resemble small trees or flowers. They release spores that grow into gametophytes. Gametophytes produce sperm and egg cells needed to produce a zygote (fertilized egg)

Seedless Vascular Plants

• In seedless vascular plants (ferns), sporophytes produce spores that develop into gametophytes. However, fern gametophytes have both male and female structures that produce sex cells. When fertilization occurs, a new sporophyte begins to develop.

Other Vascular Plants

• Other vascular plants are gymnosperms (cones) and angiosperms (flowers). The male gametophyte in both plants is called pollen, which contain cells that develop into sperm cells. For reproduction to occur, pollen must travel to the female gametophyte so it can fertilize the egg.

Asexual Reproduction in Plants

• While most plants reproduce sexualy, many plants reproduce asexually. New plants can grow from the leaves, stems, or roots of a parent plant (ex: potato eyes)

Gymnosperms

• Gymnosperms have needle-like leaves, deep roots, cones, and unprotected seeds. Male cones hold pollen, and female cones hold an ovule (the structure holding an egg). The pollen can be transported by the wind and stick to the female cone due to a sticky liquid. When this happens, the egg may become fertilized, and a zygote develops into a plant embryo in the seed. Once matured, the female cone opens up, and the wind blows the unprotected seeds out.

Angiosperms

• Angiosperms have either flowers or fruits that contain seeds. The male reproductive structure is called the stamen, including the anthers (which forms the pollen) and filament. The pistil, the female reproductive structure, has 3 parts: the sticky stigma, the style, and the ovary.

Angiosperms (cont.)

Some angiosperms are pollinated by the wind, but most rely on pollinators, or animals that spread pollen. When pollen falls on the stigma, fertilization may occur. The zygote then develops into the seed's embryo. Colorful, often pleasantly-scented petals surround the plant's reproductive organs and attract pollinators. The sepals protect the growing flower. The flower can also develop the fruit (the ripened ovary and its seeds).

Animal Behaviors

• Behavior is the way an organism reacts to changes in its internal conditions or external environment. Behaviors are adaptations that can be learned, or are an instinct, a response to a stimulus that is inborn. Learning is the process that leads to changes in behavior. The goal of animal behaviors is survival and reproduction.

Mating Behaviors and Systems

The drive to mate developed in animals as a way for their species to survive. The behavior patterns related to how animals mate are called mating systems. Monogamous animals mate with only one organism, while in other animal species, animals mate with numerous mates. (Polygyny - One Male; Polyandry - One Female; Polygynandry - Multiple)

Communication

• Animals communicate in many ways, using sounds, scents, and body movements, with the goal of reproduction. Many birds sing to attract mates, while other animals release pheromones (chemical scent released by one animal that affects the behavior of another animal; moths).

Competition

• Aggression is a threatening behavior used by some animals to intimidate another animal (for access to mates, food, or water). Another competitive behavior is establishing territory (an area occupied and defended by an animal or group; for mates)

Reproductive Strategies/Fertilization Strategies

• Different animal species have different ways of caring for their young. Some species have no contact w/ their offspring (tadpoles, snakes), while others care for them for many years (birds, mammals). Offspring that do not receive parental care must be able to care for themselves. These animals typically have many eggs in order to ensure that some will live. Mammals, like humans, are usually helpless for a while after birth. Typically, animals that provide parental care have fewer offspring (since they are protecting and nurturing them).

External and Internal Fertilization

• In sexual reproduction, a new organism forms when a sperm and egg cell are joined in fertilization. Fertilization can happen in two ways: externally or internally. External fertilization happens outside the body, and internal fertilization occurs inside the body. When internal fertilization occurs, the fertilized egg can develop inside (mammals) or outside (birds) the body.

Cooperative Behaviors

• Animals can increase their chances of survival and reproduction when they live and work together. One benefit of living in a group is that it is an effective way to protect young animals from predators (elephant circles). Other groups share parenting responsibilities of animals that are not their offspring (bees).

Migratory Behaviors

• Migration is the regular seasonal journey of one animal from one place to another. Animals migrate for food, climate, and to a better area for reproduction. Animals often follow patterns of reproduction so that offspring are born in favorable times (polar bears).

Growth and Development of Organisms

• Several factors influence how organisms grow. Some are genetic characteristics, while others are related to access to resources, the environment, or responses to stimuli. To increase their chance for survival, plants and animals adapt over time.

Plant Responses & Tropisms

• Hormones control a plant's response to stimuli (ex: Auxin speeds up the rate at which plant cells grow and controls a plant's response to light). A plant's growth response toward or away from a stimulus is called a tropism (ex: touch, gravity, light). Plant vines show positive thigmotropism (response to touch) as they coil around an object for support. A plant's response to light is called phototropism, where leaves, stems, and flowers grow toward it. A plant's response to gravity is called gravitropism. (roots show positive g., stems show negative g.)

Seasonal Change

• A plant's response to seasonal changes in the length of day and night is called phototropism. Some plants change based on the length of night, while others don't change at all. As winter approaches, many plants go into a state of dormancy, a period when an organism's growth or activity stops. This helps plants survive freezing temps and a lack of water. Cooler weather and less sunlight causes leaves to stop making chlorophyll. As a result, yellow and orange pigment becomes visible.

Environmental Conditions (Plants)

• In ideal conditions, plants will reach a maximum size that is normal for its species. However, sometimes a lack of resources can affect growth. Plants need sunlight, water, and nutrient-rich soil to grow properly. Disease can also affect how a plant grows.

Animal Growth

• A growing embryo is called an embryo (can develop inside or outside the mother's body). 1.) One way embryos develop is inside an egg that is laid outside the body. Most invertebrates, fish, reptiles, and birds lay eggs. The contents of the egg provide all the nutrients embryos need. The eggs of land vertebrates are called amniotic eggs, which are covered with membranes and a leathery shell.

Animal Growth (cont.)

• 2.) Some embryos develop inside an egg that is retained in the mother's body (snakes, lizards, sharks). The egg yolk provides nutrients for the embryo, and it hatches either inside or outside the body. 3.) In placental mammals (humans), the embryo grows and develops inside the mother's body. Essential nutrients pass to the body from the mother through a placenta.

Comparing Life Cycles

• Most vertebrates look like small versions of adults when they are young. Others go through major body changes in metamorphosis.

External & Internal Factors

• Many internal and external factors affect growth. Internal factors include genetic and hormonal characteristics. External factors include the environment (which animals have no control over).

Environmental Conditions (Animals)

• Environmental conditions include access to resources, nutrition, and space